The President's Report

This is the fifty-fourth year in the life of the Carnegie Institution of Washington. It is two years beyond a half century since, under its new Articles of Incorporation, the Institution's affairs were placed under the control of a Board of Trustees and it assumed essentially its present form and function. In the intervening fifty years there have been minor adaptations of form and there has been an extraordinary enlargement of scope and of significance, but there has been remarkably little change in the structure or the basic orientation of the Institution.

By any American standard, fifty years is a long span. By the standards of American scientific research, it is an epoch. When the Carnegie Institution was founded, it is not too much to say that in America even the idea, let alone the practice, of scientific research in its investigational, nonengineering sense had scarcely been born; and the notion of scientific investigation except as an integral but subsidiary part of university work was so strange as to be unpalatable. An archive which the Institution may properly cherish is an editorial in *Science* for 1903, expressing the gravest doubts about the function or the future of an organization devoted to such an idea. The industrial laboratory was not to appear in America in its modern form for some five more years, and it would be at least another twenty before that pattern of research would become common. To be sure, a few internationally eminent men of science were at work in American universities: Josiah Willard Gibbs at Yale, Alexander Agassiz at Harvard, himself an early Trustee of the Carnegie Institution, and the remarkable group already assembled at the Johns Hopkins come readily to mind. But in the world scene American science had a decidedly minor place, and in magnitude it was relatively insignificant.

In such a setting an organization endowed with the generosity of Mr. Carnegie's gift and devoted to the furtherance of scientific investigation

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could hardly fail to have a major impact, for good or ill. It lay within the
Institution's power to change an already existing trend in American science, or
to initiate a new one, simply by a direction of substantial funds. Strokes of
genius and serious errors of conception and planning alike could be multiplied an
hundredfold.

It is remarkable that in the face of this grave responsibility, with little
American tradition for guidance except that provided very indirectly from the
universities, a plan of operation for the Institution was devised and executed in
1904 which seems in retrospect to have been uniquely effective among the possi-
bilities that were open. The plan embodied three decisions that were to set the
whole character of the Institution: the decision to direct its activities to
investigation as distinct from teaching, except for such incidental teaching
activity as might further the general research effort; the decision to make of
the Institution primarily a "working" rather than a granting body; the decision
to organize the work of the Institution into departments, geographically dis-
persed through the country and so placed as to have ready access to a number of
the leading universities. The early history of Institution activity has left
no doubt of the extraordinary wisdom of these choices. It is interesting and
important to consider how well they have weathered an almost incredible half-
century of scientific development in this country, and how relevant they are today.

It is hard to imagine more radical changes than those in the American scien-
tific scene since those early days of the Institution. There have been two major
wars, in each of which American survival was at stake. The first was America's
real introduction to the place of technology in warfare. The second witnessed
that revolution in the concept of the nature of national security and the role of
technology in the defense of the free world which--but ten years later--is so
universally accepted today. Never, in terms of its basic philosophy, its tra-
dition, its mode of work, or its organization, has the Institution been designed

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for or adjusted to applied research; yet it was able to play an important part
in the technological change. In the First World War it made major contributions
to American military research and planning by virtue of its fund of basic knowl-
edge, its flexible form of organization, and its will. In the Second World War,
the Institution, through the vision and the action of its President and the Office
of Scientific Research and Development, served as the home of the greatest inno-
vations of our time in scientific organization and execution for war and defense.
On the technical side, some of the most important ideas in modern weaponry derive
from those years. On the organizational side, a considerable number of the great
contemporary government organizations for science take their genesis from this
same period and in this same activity. It would be hard to find a milieu further
removed from the original world or conception of the Institution in 1904 and 1905.
And yet the large decisions taken then stood the test of national emergency, and
stood it well. What of the greater test of the non-crisis years, when the Insti-
tution was freed for its own proper task?

The change involved in transition from a world of free scientific investi-
gation to an emergency one of developmental technology, rigidly applied under
the time scale and the ruthlessly uncompromising conditions dictated by the
challenge of survival itself, was severe and radical enough. But I doubt whether
it exceeded the contrast between the scene of normal uncommitted American scien-
tific research in 1906 and that in 1956. Scientific leadership is an intangible
and protean thing, difficult to evaluate at any moment and, because of the nature
of research itself, ever changing from year to year. But it is probably fair to
say that in 1956 American science, considering its quantity and quality together,
may lay claim to world leadership. In the universities, in multifarious indus-
trial research laboratories, in government, scientific research is being prosecuted
in quantity and quality such as the world, let alone our own nation, has never
known before. It is not only that with the explosive expansion of university

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facilities which is in full course today we are making better use of the native
abilities of our younger population and may expect to do still better in the
future, and thus have greatly broadened the base from which American scientific
talent may come. It is not only that we have benefited incalculably in recent
years from those brilliant minds of Europe and of Asia that have chosen to make
America their home. The most conspicuous element of all, perhaps, is a quality
inherent in the structure of science itself which has come to prominence in these
years. It is the exponential character of the rate of accretion of information
when not only the techniques of seeking new knowledge are developed, but also
systematic means for formulating the very questions by which new knowledge shall
be sought and found are devised. And we are full-tide, now, in this explosive
phase.

Against this vast and dynamic background the Institution continues to pursue
its aims of research toward the same goals, and essentially in the same manner, as
it has throughout its working life. It can bring far greater stores of experi-
ence, and in absolute terms even slightly augmented material resources, to the
task. Over the immense transition from peace to war--from an isolated America,
almost a frontier land in her concept of science, secure in the protection of
a British navy, two vast and relatively invulnerable seas, and a waste of empty
sky, to an embattled America deep in a predominantly technological struggle for
her very life--the organization and the traditions and the purposes of the Insti-
tution were such as to allow it to play a significant role. Is this also true of
the yet greater transition that a half century of science, and a major transfor-
mation in the scale and structure of American society at peace, have wrought?
There are many reasons for believing that those goals for the Institution, and
even the broad manner of achieving them, which were selected and established
fifty years ago are as relevant to leadership in the present scene as they have

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ever been. Let me examine some of them.

The Institution is dedicated to the ideal of uncommitted scientific investigation, to the scholarly search for scientific truth wherever it may lie, without primary consideration of its use in any practical sphere. Such use, of course, is neither precluded nor to be ignored. Many practical "firsts" in American technology have come from this sort of uncommitted investigation in the Institution: hybrid corn, the basis of modern cement manufacturing methods, important innovations in refractories for steel plants, the initiation of Pyrex glass, the first intimations of the principles of radar, to name but a few. Yet, important as they are in a practical sense, they are incidental to the main objectives of the Institution programs, and primarily illustrative of the widespread paradox that the most important practical consequences are commonly the least sought after.

The Institution's dedication to the role of the uncommitted investigator has further corollaries which are of real importance in the current American scientific scene. It implies dedication to investigatory work of the highest quality and takes as its objective, among other things, the maintenance of research standards. It implies great flexibility, a willingness to ignore the boundaries of established fields and to seek knowledge in those rich borderline areas that so often lie between them, a readiness to ignore conventional limitations and to follow the truth where it may lead. Above all, it implies a resolution to foster and to pay tribute to that kind of inspiration and sense of fitness in creative thinking, to the ideal of balance and proportion, which in other fields has sometimes been called a "sense of style." These are precious goals.

A series of investigations has recently been undertaken in England by Derek J. Price, seeking to gain some measure of the rate of increase of the volume of scientific effort. The criteria were chosen somewhat arbitrarily and partly for their manageability, but they embraced a series of generally related quantities,

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such as the total of registered scientific manpower, the annual expenditure on scientific matters, the number of scientific patents, the volume of scientific journals. These are admittedly rough and often partially erroneous criteria, and they give little indication of quality. The interesting thing, however, is that nearly all of them show the same general growth trends, and that these trends are essentially exponential. Moreover, the constant of the exponential curve is found to effect a doubling of the volume of scientific effort in approximately every ten to fifteen years. This is not basically a new phenomenon. There is evidence that the total amount of the scientific effort has been increasing exponentially since the time of Newton. But, as Price points out, the present rate of doubling for the total magnitude of scientific effort--two or perhaps even three times in a generation of men--is appreciably greater than that for many non-scientific and nontechnological activities. There is no reason to assume that the rate of growth of scientific effort will change from exponential to linear in the immediate future.

Among the many implications of this situation, two seem of particular importance to the present and future role of the Carnegie Institution of Washington. The first is one specifically pointed out by Price, though generally long recognized in many fields. When an attempt was made to evaluate the rate of increase in scientific attainment of the highest quality (and admittedly the yardsticks are exceedingly intangible here), it developed that this rate was considerably lower than that for the volume of research as a whole. As Price estimates in his English survey, its volume takes about three times as long to double. In this country reliable comparison is almost impossible because of the difficulty of definition. It seems likely, however, that the discrepancy is if anything greater because of the American tendency, especially since the Second World War, to label a great deal of technological effort as research which is in fact

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engineering development. Thus the field of uncommitted research of the highest quality, with which the Institution is primarily concerned, is both very much smaller and of slower rate of growth than the scientific effort as a whole. This means, of course, that the Institution remains, in a purely material sense, a larger factor in this field than in the wider one. But there is a much more important and more relevant aspect. In science as in other creative endeavors the small percentage of innovational effort of the highest quality carries significance both in its own field and in society as a whole far beyond its absolute magnitude. It is therefore peculiarly important. It is also especially vulnerable, for, however much its merit for the future may be recognized, it must always wage a continuing struggle to maintain its contemporary integrity, partly because of its deficiencies of magnitude, partly because the motivations of such work, spiritual and material, are not easily communicated at the time when it is in progress. And so the dedication of the Institution to standards of the highest quality in research, and research people, constitutes an important leadership function for the present and the future.

A second implication has to do with scientific specialization and its consequences. The antithesis between wisdom and knowledge is a truism. Yet it comes home with peculiar force in respect of scientific matters. The pressures that make for specialization in science are many and compelling. Specialization, in a very real sense, is the life blood of scientific investigation. Only the specialist, the investigator who has spent years with his limited subject in its most intimate detail, whose mind and whose eye and whose whole being are attuned to its peculiar subtleties, is in a position to grasp the opportunities that lie deeply hidden, to achieve the truly significant insights. Except for the occasional genius of the caliber of a da Vinci, it is only to such men that real penetration can come. It is still as it was said by Pasteur: "In experimentation,

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chance favors only the prepared mind." This is perhaps the most compelling, and indeed the most essential, of the reasons for scientific specialization. Other reasons are scarcely less important. It is only to those who have won mastery of their subject that the full satisfaction and joy of creativity belong. It follows that these rewards, the most powerful incentives to research, can come only to him who, in some measure at least, is a specialist. And to the specialist in the company of his fellows belong those other rarest of working rewards: encouragement, reinforcement, solidarity, the powerful spirit of a truly understanding working fraternity.

But the pernicious effects of unchecked specialism are notoriously legion. As specialties diverge and grow--and their rate of divergence is in keeping with the rate of growth of science as a whole--they become vastly remote from one another, as disparate as the points of the compass. In the early stages this divergence may be one principally of language. But in actively growing fields the alienation quickly extends to the very concepts for which the words stand. In the end, divergent specialties may differ as much, in language, in mode of approach, in basic orientation, in systems of values not only about their own subject but about the world in general, as two different cultures. Once these differences are firmly established, strong barriers arise to the crossing of boundaries. The specialist now is professionally identified with his specialty. It is but human to adhere to it tenaciously in virtue of its own name and rubric, and to be hostile to other areas of knowledge that are now not so easy to understand or to appreciate. The whole matter of professional identification with other members of his specialty as distinct from workers in adjacent fields, in postgraduate and in later professional life, adds a final practical compulsion to the isolation of the specialist. To a dangerous degree, he has sacrificed his flexibility. And so is maintained and ever emphasized that bane of our times

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which follows so naturally from the accretion of knowledge, which is so anti-
thetical to true wisdom, of which we are so conscious but about which we have yet
been able to do so little--excessive fragmentation.

There is much evidence of a widespread growing realization of this peril,
and there is a great need for leadership in combating it. Specialization can
never be avoided; it is a keynote of scientific expansion and of our technologi-
cal civilization. But the ideal can be emphasized of the superior individual
whose capacity, whose training, whose judgment, and whose orientation will be
those of the generalist, without loss of the discipline or the competence of the
specialist. It is not an unattainable ideal. Men of high quality and aspiration
have reached it before.

The Carnegie Institution, by virtue of its tradition and its structure, is
particularly well placed to give leadership here. It has always been a funda-
mental part of the Institution's policy that the subject areas in which it worked
should be chosen with great flexibility, that the rubrics of the departments should
not be taken rigidly to restrict their subject matter, that investigations of
areas considered by competent men to be of great inherent interest should be fur-
thered whether they fell within conventionally recognized boundaries of scientific
disciplines or squarely between them, that every encouragement should be given to
the taking of long intellectual risks by those equipped to do so. Of recent
years some of the most exciting and profitable investigations in the Institution
have fallen between the fields of physics and astronomy, or of biology, chemistry,
and physics. It has always been Institution policy that the work of its staff
should be evaluated in terms only of the mature and collective judgment of their
peers, and never by those conventional standards which too often tend to solidify
the boundaries of specialties and break down understanding between them. There
is an important task to be performed both in demonstrating that specialization is

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the necessary servant, but must not be the master, of a discipline, and in
training future leaders in scientific research to whom this truth is familiar and
accepted.

These are the answers to the question whether the goals and the method of
approaching them which were established for the Carnegie Institution more than
fifty years ago are still relevant today. The functions of the Institution in
the coming years must be what they have always been: to stimulate scientific
research of the highest caliber, to conceive and open new areas of research which
can later be taken up by others, to provide advice and guidance in scientific
matters at the most effective levels of national policy, but, above all, to enrich
the national resources of research personnel and the conception of research stand-
ards and their goals. Once it was the relative amount of Institution activity
that counted most heavily. Now it is a matter of philosophy, and of quality.
And here, once again, the first key decisions stand valid.

In such a context the Institution must remain, as it has been throughout its
life, primarily an investigative and primarily a working body. For no group
that aspires to set standards in the scientific community is entitled to respect
or can carry conviction unless its own house demonstrates actively and unequiv-
ocally those standards to which it is dedicated.

This is the root from which many other means of leadership and of communi-
cation, chosen flexibly as circumstances dictate, may stem. The dispersion of
the departments of the Institution and their proximity to leading universities,
both geographically and in fields of work, offer great opportunities in many
important sectors of scientific activity other than substantive research. But
the whole effort will have validity, and conviction, only to the degree that it
remains firmly based in the programs of uncommitted research of high quality and
fresh interest going forward within the Institution. They are the essence of a
very precious way of life.

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# The Year's Work in Review

## The Scientific Program

It is always difficult to select individual researches of the year for special mention. It may be misleading to do so without emphasizing that the programs so selected are taken only as examples of the kind of work that has been going forward in the various departments during the year. Their mention in this summary review implies only their representative interest--it cannot imply that they are either more or less striking or important than many other programs that might have been described. The reader who is especially interested in the work of any department should turn to the fuller review of its work later in the report.

This year marks a point of particularly vivid interest in the programs of the Mount Wilson and Palomar Observatories which are concerned with the nature and extent of the universe. In the second decade of the century, W. M. Slipher, at the Lowell Observatories, measuring the spectral redshifts of a number of stellar objects, showed that they were receding from us at great speeds. Edwin P. Hubble, at Mount Wilson, establishing that these objects were actually systems of stars, measured the distances of many of these nebulae and demonstrated not only that some of them lay at far greater distances from us than had been imagined, but that their velocities of recession, as measured by their redshifts, increased strictly in proportion to their distances. This was the basis for Hubble's now classic hypothesis that the universe as a whole is expanding, and his prediction that more remote galaxies, as they were examined, would show yet larger redshifts, and in proportion to their distances. Ever since that time, study of this phenomenon has continued, especially by Humason at Mount Wilson and Palomar. In 1936 the limit of range of the 100-inch telescope was reached, and Hubble's prediction was fulfilled--all the way out the redshift increased in

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proportion to the distance, suggesting a uniformly expanding universe. When the 200-inch telescope became available at Palomar, the program was resumed with new spectrographic equipment. Redshift measurements of clusters of galaxies with velocities of recession up to 60,000 kilometers per second have now been accomplished. Far out, the linear proportion held. But clusters about a billion light-years removed are found to be moving faster than in direct proportion to their apparent distance. If confirmed, such data can be interpreted to mean that a billion years ago the universe was expanding *more rapidly* than it is at present. To test this further, the current redshift program is confined to observation of faint galaxies in the most distant clusters that can be found and observed--a difficult technical achievement. Two such clusters, with predicted redshifts greater than 100,000 kilometers per second, have already been observed by Humason, and measurements of the spectra indicate that the shifts for both are probably large and of the right order. If the measurements and interpretation are verified, they suggest that our universe is an evolving rather than a steady-state one. They may allow conclusions of a fundamental and far-reaching nature about the geometry of space, and about the mean density of matter in the universe. The present observations, for example, are in conflict with the concept of a steady-state universe as conceived by Hoyle and by H. Bondi and T. Gold. They require an expanding model of finite dimensions and with a positive radius of curvature. The expansion will eventually stop, and contraction will set in. The universe is of the so-called oscillating type. It may well be that the studies begun by Hubble and Humason three decades ago will reach a most important--and indeed most dramatic--climax in the next year or two.

A second program of great interest at the Observatories is concerned with problems of stellar evolution. How are stars formed? What is their lifetime? How do various observable properties, such as absolute brightness, surface temperature, and chemical composition, change during this lifetime? According to present concepts, stars are formed originally by the condensation of clouds of

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material, principally hydrogen. As the cloud contracts into a star its core heats to temperatures at which transformation of the hydrogen to helium takes place. This nuclear fusion reaction produces very large quantities of energy, which in turn are radiated away at the surface of the star. A point is soon reached in which the generation of energy is just balanced by radiation loss. In this initial steady state both the brightness of the star and its surface temperature vary sharply with the mass. A star with a mass twelve times that of the sun gives off 1000 times its light and has a surface temperature of 23,000° C--four times that of the sun. At the other extreme, a star with a mass one-seventh that of the sun radiates at one-tenthousandth of the rate and has a surface temperature of only 3000° C. Stars that are in this initial state of equilibrium between energy generation and energy loss through radiation, and which maintain this relationship between mass, luminosity, and surface temperature, are said, in evolutionary terms, to be on the main sequence.

As time goes on, the hydrogen fuel of these stars is depleted. Eventually their composition becomes so changed that the equilibrium of energy generation and dissipation is upset. Theory predicts that, when this occurs, the star will slowly expand, its surface will cool, and it will appear redder. At the same time its rate of energy radiation will actually increase. Then, as the hydrogen fuel is still further exhausted, the process is reversed, the star contracts and grows hotter, but also fainter. At one or more stages in this evolution the star becomes unstable and pulsates rapidly with a corresponding oscillation in brightness. Eventually, when the fuel is completely exhausted, the star stops radiating and can no longer be observed.

This picture of stellar evolution provides an explanation for the observations on different types of stellar populations which have been carried forward by Baade for a number of years and have been reported in previous Year Books. Thus, for example, huge clouds of gas and dust are observed in the spiral arms of our own Galaxy and of the Andromeda galaxy where Population I stars predominate. These

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clouds are still condensing to form stars, and in these arms, young, comparatively
newly formed stars abound. The most characteristic features of such "young"
populations are very massive, exceedingly bright, and very hot blue stars.

By contrast, in the central regions of the galaxies where Population II
stars predominate, the stars must be, comparatively, "ancient," having been
formed billions of years ago from dust or gas clouds which have now completely
vanshed. All the very bright blue stars have used up their fuel and dis-
appeared: they are not represented in these "old" populations.

It is evident that there will be a difference in the rate of evolution be-
tween the very bright stars, which are using up their hydrogen fuel rapidly, and
the faint stars, which are using theirs at a slower rate. The brightest stars
of the old Population II groups, therefore, are the stars of intermediate
brightness that have just reached the stage where they expand and cool but at
the same time become brighter. The most conspicuous stars in this population
are therefore cool and red.

This is the broad picture--suggested by Baade's discoveries of Population I
and Population II. But many parts of the theories must be refined and filled
in, and extremely active work is in progress, theoretical and observational,
both at the Institution and at the California Institute of Technology, to this
end. One example of many such researches currently in progress at the Obser-
vatories is offered by investigations on the relationships between the absolute
brightness and the surface temperature, as indicated by the color index, for
stars in a number of clusters. A comparison of the shape of, and distribution
along, the color-magnitude diagram thus obtained with the color-magnitude dia-
gram of the main-sequence stars yields information on the manner in which the
properties of stars of various masses change with age, and the rate of such
change. Extensive spectroscopic investigations are in progress on main-sequence
stars and also on stars in the globular clusters to determine their chemical

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compositions for comparison with the predictions made from laboratory studies of reaction rates. The combined result of all these laboratory, theoretical, and observational studies is leading to a greatly expanded understanding of stars, the source of the energy they radiate, and their evolutionary history.

The year has also been a profitable one in the new field of the study of stars as radio sources. One of the outstanding events of last year was the explanation of the light emission in the Crab Nebula (the remains of a supernova, the explosion of which is recorded in Chinese annals in A.D. 1054) as due to electrons circling in a magnetic field--a situation similar to that in the synchrotron and so known as the synchrotron mechanism. Since, according to this theory, strong polarization (up to 100 per cent) was to be expected in the continuum of the Nebula, a test at the 200-inch telescope seemed especially desirable. Measurements of such effects made by Baade reveal marked polarization, in accordance with theory, and this finding has been confirmed by Baum and by Zwicky, using different methods. Similar confirmations of theory are suggested in another celestial object in which the synchrotron mechanism is believed to be operative--the jet in the M 87 galaxy. Both the Crab Nebula and M 87 are strong sources of radio noise and have continuous, as opposed to emission, optical spectra. These conditions are theoretically explicable on the basis of the synchrotron mechanism.

The present year has seen the completion of the National Geographic-Palomar Observatory Sky Survey, generously financed by the National Geographic Society. The whole sky accessible from Palomar Mountain has been photographed in both red and blue light--a labor requiring for its completion almost the whole observing time of the 48-inch schmidt camera for seven years and using 879 plates in each color. The blue plates reached a limiting magnitude of 21.1, two or three magnitudes beyond that of any previous survey of the whole sky, allowing an increase in this survey by a factor of about 3 in depth penetrated and of about 25 in total volume of space recorded. Many new objects of great potential interest

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have been found, the full study of which will require many decades.

Of more intimate interest to us than the ages and rates of evolution of
the stars in distant galaxies is the age of our own earth. One clue to the
determination of the age of the earth comes from the measurement of radioactive
decay in ancient rocks. Early in the century, the radioactive decay of uranium
and thorium was recognized as a useful yardstick in making such measurements.
It presented certain difficulties, and in more recent years other radioactive
decay chains have been investigated, offering widened possibilities for corre-
lation and for checking.

For several years past the staffs of the Department of Terrestrial Magnes-
tism and the Geophysical Laboratory have joined in a critical study of such
methods of measuring the ages of minerals. Special attention has been given
to the new methods available in the natural radioactive decay of rubidium (to
strontium) and of potassium (to argon).

It has been found that for pure mica crystals separated from almost any
igneous rock the two ages obtained from the decay of potassium and rubidium
agree within 10 per cent. Further, when it is possible to determine unambigu-
ously the age of the rock from the radioactive decay of uranium to lead, the
potassium-argon and the rubidium-strontium figures of the mica agree with the
uranium-lead ages. For many igneous rocks the ages from the decay of uranium
to lead do not agree. In all such cases that have been studied it is found
that the potassium-argon and rubidium-strontium ages of mica from these rocks
still agree. It looks very much, therefore, as though accurate ages may now
be obtained for many geologic formations which previously could not have been
measured. Indeed, these new methods for dating igneous intrusives and inclu-
sions in ancient sediments may make it possible to place even these formations
in an absolute time sequence. World-wide correlations of pre-Cambrian

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sedimentary formations would then become a real possibility for the first time.
The methods have already established that sedimentary and volcanic formations
older than 2500 million years occur on the North American, Australian, and South
African continents.

Changes in the nature of the earth's crust with increasing depth have long
been of interest both to the Department of Terrestrial Magnetism and to the
Geophysical Laboratory. For some years past the Department of Terrestrial
Magnetism has conducted a series of seismic investigations in the field, recently
ranging as far as the Alaskan peninsula, to investigate interesting and signifi-
cant crustal discontinuities. Parallel laboratory experiments have been con-
tinued at the Department by Tatel and his associates. Recently a very inter-
esting new approach to the whole problem of the nature of underlying causes of
the Mohorovičić discontinuity has been suggested by work at the Geophysical
Laboratory. A study of phase changes occurring in certain rock minerals under
conditions of temperature and pressure simulating those under natural conditions
in the vicinity of the Mohorovičić discontinuity suggests that the discontinuity
may be primarily the result of sharp phase boundaries, sensitive to small shifts
of temperature and pressure, in that region. This is a very different concept
from the older one that the discontinuity is primarily the result of changes of
chemical composition with increasing depth. So revolutionary may its impli-
cations be, in fact, in relation to such matters as the mechanisms of mountain
building, that extensive further laboratory investigation of these phase-shift
phenomena seems urgent. Accordingly, phase changes have been studied this year
at the Geophysical Laboratory at pressures as high as 60,000 atmospheres and
temperatures up to about 700° C, using equipment built by Boyd and England.

With this apparatus dense minerals have been artificially produced such as might
exist naturally deep in the earth. Exploratory experiments of this kind have been
conducted in Feldspars, Feldspathoids, and denser minerals. Transitions
have

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been found to occur in nepheline, leucite, and anorthite. Anorthite is particu-
larly interesting, since it is common as a component in plagioclase in deep-
crystallizing plutonic rocks, and its breakdown deep in the crust might well con-
tribute to the Mohorovičić discontinuity.

Continuing investigation of the composition of minerals in the earth's crust, Eugster at the Geophysical Laboratory has synthesized pure iron-bearing mica annite and has opened new areas of opportunity in mineral synthesis. He has determined the field of stability of this mica as a function of temperature, oxygen pressure, and water pressure, and has shown that even a small increment of oxygen pressure may drastically lower the breakdown temperature of the mineral.

The first determinations of stability of a sulfide mineral under pressure have been made by Kullerud and Yoder. Using a new technique of general applicability, they have studied the upper stability curve of pyrite (FeS₂). It proves to be stable below 815° C at a pressure of 5000 bars. These experiments help to explain why primary pyrite occurs in deep-seated granites and amphibolites but not in basalts or in rhyolites.

Varied fundamental investigations of the nature of life and life processes continue to attract the attention of five departments of the Institution--the Department of Terrestrial Magnetism, the Geophysical Laboratory, and the Departments of Genetics, Plant Biology, and Embryology. At the Geophysical Laboratory, Abelson, continuing his pioneer work on the existence and nature of very ancient and primitive life, has shown that amino acids such as glycine, sarcosine, alanine,

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and β-alanine can be formed from a variety of "primitive atmospheres." Simulating conditions that might have been present in the early history of the earth, he has subjected gaseous mixtures to electrical discharges. Among the combinations yielding amino acids were: CO₂ - N₂ - H₂ - H₂O; CO₂ - N₂ - H₂ - H₂O; CO₂ - NH₃ - H₂ - H₂O; and CH₃ - N₂ - H₂O.

Studies of certain fundamental aspects of metabolism in microorganisms are continuing at the Department of Terrestrial Magnetism. From the beginning, these studies focused about the problems of protein and nucleic acid synthesis at the molecular level in intact cells growing exponentially in synthetic media. Two very different types of microorganisms have been used in this work, contrasting greatly in complexity--the bacillus *Escherichia coli* and the yeastlike *Torulopsis utilis*. For several years the studies were concentrated on the synthesis of small molecules by these organisms: amino acids, purines, and pyrimidines, which serve as building blocks for the proteins and amino acids. Last year and this, investigation has progressed to a study of the ways in which these blocks are incorporated.

In general, the first step in such synthesis is for the cell to concentrate the small molecules into a relatively loosely held "pool," where they are held, and subsequently linked into the macromolecules. The past year's work has greatly increased our knowledge of the characteristics of these pools. In addition, some of the immediate precursors of nucleic acid have been determined and an upper limit for the time required for protein synthesis has been established. It is three seconds.

Studies of these pools of synthesis for proteins and nucleic acids have been of direct interest to the investigations in bacteriophage metabolism at the Department of Genetics. Here, however, interest has been centered primarily on the intact nucleic acid in the phage itself, on its mode of transfer, and on its

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role in heredity.

Previous work by Hershey and his collaborators, utilizing radioactive tracers, had shown that the main body of a bacterial virus particle is made up of deoxyribonucleic acid and that the coat surrounding the body contains protein. These workers had also demonstrated that the DNA transmits viral hereditary characteristics. During the past year they have obtained evidence from two new experimental sources that large, functionally intact pieces of viral nucleic acid may pass from parent to offspring phage. If bacteria are infected with a mixture of ultraviolet-irradiated and nonirradiated phage particles, a small number of noninfective offspring particles is produced. These particles contain a high concentration of nucleic acid derived from the irradiated parent. Thus radiation-induced lesions must be transmitted from parental to offspring particles in the form of large pieces of irradiated parental nucleic acid. Again, if bacteria are infected with two kinds of phage particles, differing both in their genetic markers and in their labeled phosphorus, about two-thirds of the parental phosphorus remains associated with the parental genotype during transfer from parent to offspring phage. Both results suggest that part of the viral nucleic acid is contained in a functional chromosome that is not subject to progressive fragmentation during replication and genetic recombination.

A bacterial cell is much more highly organized than a bacterial virus particle. Quite powerful biological methods have been developed, however, for investigating the genetic properties of certain simple unicellular organisms. One of the most sensitive of these makes use of the phenomenon of "transduction." This is the transport of fragments of genetically active material, presumably small segments of chromosome, by infective virus particles, from the bacterium in which the phage have been raised into the bacteria which they subsequently infect. Demerec and his collaborators have used this method to carry out penetrating genetic analyses of short regions of the chromosome complex of

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**Salmonella typhimurium.** Their studies have demonstrated that the "gene" as previously defined is not the ultimate hereditary unit but can be broken down with these finer analytical tools into yet smaller entities (sites), linearly arranged in a definite order. During the past year it has been shown that mutations occurring at different sites of a single locus, although they affect one function primarily, may produce mutants that differ considerably from one another with respect to various properties.

Several years ago McClintock demonstrated the existence of certain heritable units in the chromosome complement of maize that served to control and modify the effects of other genes, without themselves directly affecting the phenotype. Knowledge of such elements has been considerably expanded during the past year. A number of these units, now called "controlling elements," have been identified and their distinctive modes of operation examined. It is now evident that they may act not only as mutators, but also as inhibitors, suppressors, enhancers, or other kinds of modifiers of gene action. They may shift from one location to another within the chromosome complement without losing their identity in the process. A further effect, involving a structurally modified chromosome in the presence of which marked changes in chromosome organization and also in gene action take place, is also under investigation.

Kaufmann and his associates have continued their studies on patterns of chromosome organization. They have interpreted electron micrographs of salivary glands of *Drosophila* and of dividing cells of *Tradescantia* as indicating that the chromosomes patterns of organization of these represent a hierarchy of pairs of helically disposed chromonemata. In *Tradescantia* there are at least 64 (and probably 128) subsidiary units in the somatic prophase chromosomes of the staminate-hair cells. It has been concluded, from studies of the effects of various chemicals such as ribonuclease, ethylenediaminetetraacetic acid, and calcium chloride on *Drosophila* and onion roots, that any agent which disrupts the normal metabolism

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of the cell can lead to instability that is reflected in modification of chromo-
some form and behavior.

Several years ago a particularly interesting phenomenon was discovered with
the electron microscope, involving a curious "blebbing" of the nuclear membrane
into the cytoplasm. Gay has now determined the stage of development of the
salivary-gland cell in *Drosophila* where this takes place and has found that it
is correlated with the assumption by the cell of a new function. This finding
gives strong support to the hypothesis that nuclear-membrane blebbing is a mani-
festation of a new mechanism for genetic control of cytoplasmic function. It
has been found that deoxyribonucleic acid is included within the blebs, and that
ribonucleic acid constitutes part of the associated highly differentiated chromo-
somal material, adding further weight to this hypothesis.

Perhaps the two most dynamic parts of present-day genetic research lie in
the realm of physiological genetics, concerned with the organization and mode of
function of the chromosome, the whole nucleus, and the cytoplasm from an essen-
tially molecular viewpoint, and of population genetics, concerned with the organ-
ization and functioning of a whole population from the standpoint of the indivi-
duals composing it. Most of the work in genetics within the Carnegie Institution
is concentrated in the former field. However, some work in the latter is also
being carried forward in the Department of Genetics. Thus during the year Moser
completed a mathematical analysis of the dynamics of bacterial populations. The
theory provides analytical background, among other things, for the calculation of
bacterial mutation rates and specific-selection pressures, and of their standard
errors.

It is a long step from the study of biological organization at the level of
the chromosome to that at the level of the population. An intermediate level is
provided by the organization of cells that go to form a many-celled plant or ani-
mal. The interest of the Department of Embryology centers at this level, taking

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the animal embryo as the example _par excellence_ of this level of organization in
perhaps its most dynamic developmental phase.

The cellular processes occurring during embryonic development, the period
in which the fundamental character and specificity of the tissues composing the
organism are established, present a series of challenging problems. Whereas
in the adult, under normal conditions, the cells produce molecular species essen-
tially similar to those already present, during embryogenesis and under certain
other developmental conditions such as regeneration, new types of synthesis must
occur. It has been argued that chemical kinetic theory provides several differ-
ent models for systems of interacting synthetic processes which will change pro-
gressively toward one of a number of alternative steady states, the direction
depending on the initial conditions. During the year, Ebert has continued to
explore the chemo-differentiation of the heart-forming areas of the early chick
embryo. Distinct metabolic properties of an organ-forming area--the heart-
forming regions in the chick embryo--have been demonstrated for the first time.
It has been shown that antimycin A acts, in the effective concentration range,
as a specific inhibitor of heart formation. (Sodium fluoride is known to act
similarly.) These specific effects have been contrasted with the general in-
hibition of development by other inhibitors, including amino acid analogues.
A most striking finding was also made in connection with the sodium fluoride
effect. Embryos cultured in one-hundredth molar sodium fluoride for 2 to 5
hours showed marked areas of degeneration corresponding in position (at stage 5
of the Hamburger and Hamilton series) to the localization of cardiac actin and
myosin, and to the heart-forming areas as revealed by transplantation techniques.
At states 6, 7, and 8 the position of the degenerating regions reflected the
anteromedial movements of the heart-forming cells.

These provocative findings pose a series of further questions, among them:
In the region affected by the inhibitor, is the synthesis of the cardiac proteins

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blocked, or is the effect at the level of morphogenesis, on the fashioning of
the contractile elements into their characteristic structure? Is there an
alteration in the pattern of differentiation of the sarcosomes? What are the
relationships between mitochondrial differentiation and the course of muscle
fibrinogenesis? Answering these questions will be a challenging task.

An important part of the research effort of the Department during the past
year has been directed toward a fuller understanding of the critical period in
mammalian development in which the embryo is transported to the uterus, becomes
implanted, and begins its uterine career. Böving has carried on interesting
studies on the mechanism of the remarkably even spacing of blastocysts along the
rabbit uterus, hitherto very imperfectly understood. It was found that the
"spacing" was accomplished by the delicate interaction of two progesterone-
dependent mechanisms. It also seems probable that blastocyst diameter plays a
role in the phenomenon. Greenwald has taken as a point of departure for a simi-
lar investigation an analysis of the mechanism of interruption of implantation
and maintenance of the rabbit blastocyst by injected estrogen. It has been con-
firmed that (following earlier preliminary experiments of Csapo) as little as 5
gamma of estradiol daily for three days, commencing on the second day after fer-
tilization, will interrupt pregnancy in the rabbit.

Among the many other lines of investigation under way in the Department,
three further ones are of such general interest as to warrant special mention in
so brief a summary.

Bishop successfully concluded a series of studies of the nature of the fluid
of the rabbit oviduct. His research was directed toward the elucidation of the
factors controlling the release of the tubal fluid and to an analysis of its bio-
chemical composition, with special emphasis on the substrates for the metabolism
of sperm. These studies of the tubal fluid, which has been shown to be secreted
under the influence of estrogen, have revealed an absence of glucose and fructose

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but the presence of significant quantities of lactate and phospholipid. The absence of fructose, long regarded by many investigators as the normal physiological substrate for sperm, and the demonstration, through the use of the oxygen microcathode, that the interior of the oviduct presents an aerobic environment, indicate that the older idea that sperm and eggs carry on obligate anaerobic glycolysis is incorrect. In the absence of readily available tubal substrates, the sperm must utilize endogenous phospholipid reserves; this fact is believed to be one of the deciding factors in sperm survival and fertilizability.

Bartelmez has made notable progress in his analysis of the vascular changes during the menstrual cycle in the rhesus monkey. The problem is to correlate the changing pattern of the coiled arteries of the uterus with the events of the hormonally controlled reproductive cycle. On the basis of his detailed description of the vasculature of the endometrium (the lining of the uterus) Bartelmez has advanced the suggestion that the rate of blood flow determines the hormonal responsiveness of the various regions of the endometrium. He has also presented evidence that the loss of tissue from the endometrium during menstruation does not involve three-fourths of the membrane, as is usually taught. The increased contortion of the coiled arteries is a striking feature of menstruation, but it appears that only the superficial branches of these arteries are lost during ovulatory menstruation. Bartelmez argues that the reduction in thickness of the endometrium is due largely to a reduction in size in the component cells in the course of their dedifferentiation, and a diminution in mass of the intercellular ground substance.

These studies by Bartelmez are complemented by the closely related investigations of Ramsey, who, in part in collaboration with Bartelmez and Böving, has confirmed and extended her earlier conclusions concerning the vascular patterns of the placenta. She has shown that maternal blood enters the intervillous space, the terminal area of metabolic exchange between the maternal and fetal

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blood streams, from small blood vessels, the spiral arterioles, under a head of
maternal pressure. It does not "short-cut" into venous exits even when they are
contiguous to the arterial entry points along the base of the placenta. In ad-
dition, it has been demonstrated clearly that the arterial units are independent:
not all arteries contract and relax at the same time. The separation of afferent
and efferent streams is effected primarily by pressure differentials in the inter-
villous space, assisted by features of the morphological structure.

De Feo and S. R. M. Reynolds completed the first phase of a program designed
to study the effects of the alkaloid reserpine on the reproductive cycle of the
rhesus monkey. The observation, by others, that in rats ovulation may be sup-
pressed when the drug is given in proestrus suggested that reserpine might provide
an effective pharmacologic block to ovulation in the monkey, as well as in other
primates including man. Although the research must be extended to include a
study of possible seasonal variations, the initial results are provocative.
Reserpine suppresses menstruation and ovulation when it is administered throughout
the reproductive cycle; it also influences the cyclic pattern when it is given at
the beginning of the cycle, i. e., through the first twelve days. Menstruation
is suppressed; ovulation does not occur. When administration of the drug is
begun later in the cycle, however, no effect on ovulation is observed. These
observations are noteworthy not only because of their importance to a better under-
standing of the relation of the hypothalamus (through which reserpine is said to
act) to ovulatory mechanisms, but also because of their implications with respect
to the possible adverse effects of reserpine and related drugs, widely, and often
indiscriminately, used as tranquilizing agents.

The Department of Plant Biology, like the Department of Genetics, is concerned with phenomena involved in growth and development at two very different organizational levels--the level of cellular and intracellular organization and the level of the population. They are represented in the Department of Plant

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Biology respectively by an intensive study of the mode and mechanisms of photo-synthesis, and studies in experimental taxonomy. In both areas the Department has a long and active tradition.

On the first front, the year has brought some exceedingly interesting and suggestive advances. A finding which is still qualitative and preliminary, but of great interest, suggests an active participation of carotene in the photo-chemical action of chloroplasts. When chloroplasts were extracted from a leaf, frozen and dried and fragmented, and treated dry with petroleum ether as a solvent, they were found to have lost all but 10 to 20 per cent of their photochemical activity as indicated by a dye-reduction reaction. When these inactive fragments, as a dry powder, were immersed again in the solvent fraction and the liquid was evaporated, it was found that the photochemical activity had been restored nearly to normal. Activity, however, could also be restored by adding β-carotene from a laboratory supply. This experiment may well open an avenue to removing and substituting carotenoid pigments in the photosynthetic system in such a fashion that their part in photosynthesis, if it exists, can be explored.

A second investigation of great interest concerns the development of a method for measuring the transformation of protochlorophyll to chlorophyll, by spectrophotometric methods, directly in the living leaf. Hitherto, the transformation of protochlorophyll to the much darker green photosynthesizing chlorophyll, which takes place rapidly when living leaves grown in the dark are illuminated, had to be studied either by fluorescence spectroscopy of killed leaves or by subsequent extraction of the pigments themselves. Thanks to a method developed by Shibata, it is now possible to measure the complete absorption spectrum of protochlorophyll and of chlorophyll directly in the living leaf while the transformation is actually taking place. In consequence, a previously unsuspected intermediate form of chlorophyll was discovered. This new intermediate, recognized by its absorption peak at 684 μμ, is formed immediately when the dark-

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grown leaves are illuminated. Furthermore, Shibata found that this intermediate
changes in about ten minutes, without the need for further illumination, into the
form absorbing at 671 µµ which had previously been considered by some workers to
be the first intermediate form of chlorophyll. After about two hours more in
dark or light the normal form of chlorophyll absorbing at 678 µµ predominates.

Smith and Kupke have continued their basic work on the purification and
characterization of the protochlorophyll-protein complex--the "holochrome"-- from
dark-grown leaves which has been reported previously. The ultracentrifugation
methods previously described have been supplemented by a procedure employing
fractional precipitation with salts. It now seems clear that active protochloro-
phyll is attached to particles of uniform size, possessing an estimated molecular
weight of about 400,000, largely protein in character and nearly spherical in
shape. Partially purified preparations of these particles may be frozen and
dried without losing their ability to transform their protochlorophyll into chloro-
phyll on illumination. It is truly remarkable that a transformation of this kind,
so fundamental to the whole photosynthetic process in the living plant, can take
place in dry particles when illuminated as readily as if the particles were in water.

Several investigations in experimental taxonomy which have been under way in
the Department for many years are now being brought to a conclusion. In the
program involving range grasses, apomictic lines of hybrids of Poa ampla x P.
arida--a most promising combination--have been established for the first time.
New plantings of selected range-grass hybrids, to make more precise comparisons
of their climatic responses under varying conditions, have been undertaken. A
comprehensive monograph has been completed describing the genetic constitution
and the patterns of evolution of climatic races of the plant Potentilla under
various climatic and ecological conditions. Extensive experiments designed to
substantiate and elaborate ideas evolved during the past decade are throwing new

light on evolutionary mechanisms and species relationships in the yarrow, a common and widely distributed plant. Genetic experiments are in progress with species monkey flower hybrids of lowland and altitudinal races of the ^, Mimulus. Preliminary work with the tiny floating plant Lemna, common on the surfaces of ponds and quiet streams over a large part of the land surface of the world, has shown this plant to be of great interest and adaptability for various investigations in "physiological ecology." Investigations of a similar kind are also in progress with Artemisia, that widely distributed colonizer of western open lands, the sage.

Reluctantly, the Carnegie Institution has decided to leave the field of Middle American archaeology. In accordance with the decision that its work in this field will be discontinued in about two years, the Department of Archaeology has concentrated its efforts on the completion of its current program of studies. Members of the staff have this year been primarily engaged in the preparation of preliminary reports covering field work, the study of collections, and the analysis of accumulated data. The final results of these studies will appear somewhat later. A full account of their current status will be found in the report of the Department for this year.

## Losses ......

The death of two distinguished retired directors and three staff members of the Institution this year has brought a deep sense of loss.

In the *Year Book* for 1904 it is recorded that an astronomer-staff member of the Institution, Walter S. Adams, took readings at stated hours with a 3½-inch telescope to determine seeing conditions on Mount Wilson. As one of the small party that went with George Ellery Hale to set up the Mount Wilson Observatory in California, Walter Sydney Adams witnessed in the forty years of his association with that Observatory the establishment and full development of the greatest center for observational astronomical research in the world. First as Assistant

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Astronomer at the Mount Wilson Observatory, and then successively as Acting Director (1910-1911), Assistant Director (1913-1928), and Director (1924-1945), Dr. Adams played a leading part in almost every major activity. He had an important role in the planning of the 200-inch Hale Telescope and the building of the new Observatory on Mount Palomar. His death on May 11, 1956, brought to a close a most distinguished career in the field of astronomy.

Dr. Adams' chief enthusiasm and interest centered in solar and stellar spectroscopy. His early studies were concerned with the laws of the rotation of the sun, and in his spectroscopic investigations he made careful measurements of the Doppler displacements at different solar latitudes. His measurements significantly raised the level of accuracy in observations at the time, and they are still of value. In 1914 Dr. Adams was elected an Associate of the Royal Astronomical Society; in 1917 he received its Gold Medal for his studies on the determination of the absolute magnitude of stars, his interpretation of stellar spectra of different types, and the spectroscopic determination of stellar parallaxes. His later investigations in high-dispersion stellar spectra revealed important new data about the nature and motions of interstellar gases.

During World War II Dr. Adams was in charge of all work at the Mount Wilson Observatory under war contracts concerned with optics, optical instruments, aerial photography, and the efficiency of types of bomber forms. He was a Consultant to the National Defense Research Committee from 1941 to 1945. He was instrumental, too, in keeping the International Astronomical Union alive during the war, serving as its vice-president from 1935 to 1949.

Dr. Adams' scientific achievements brought him many honors, including election to the National Academy of Sciences in 1917 and awards of the Draper Medal and Bruce Medal in America and the Prix Janssen and the Janssen Medal in France.

Dr. John A. Fleming, internationally known authority on geophysics, died on July 29, 1956, at the age of 79. He had been associated with the Institution for

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a half century, joining the staff of the newly established Department of Terrestrial Magnetism in 1904, and becoming Acting Director in 1929 and Director in 1935. From the time of his retirement in 1946 until 1954 he served as Adviser in International Scientific Relations for the Institution.

Dr. Fleming was a man of amazing energy. Under his direction the Department became a leading center of research on the earth's magnetic and electric fields. One of the interesting and especially significant lines of investigation pursued under Dr. Fleming's direction was an estimation of the height of the ionized layers in the atmosphere by means of radio waves. Out of this came the Breit-Tuve pulse technique for sending and recording the return of radio waves--a technique that later became the basis for radar. One of the exciting events that occurred in the Department's laboratory during Dr. Fleming's directorship was the demonstration in January 1939 of nuclear fission, thirty-six hours after the telegram "Barium comes from uranium" came from Copenhagen to Niels Bohr, who was then in Washington, attending a conference jointly sponsored by the Carnegie Institution and the George Washington University.

During World War I Dr. Fleming worked on the perfection of a magnetic type of underwater mine that was used extensively in the North Sea area, and developed a special long-period gimbal-ring support for the mounting of a submarine detection device. During World War II, as director of the Department of Terrestrial Magnetism, he was in charge of all work under Institution war contracts concerned with ordnance devices, including the proximity fuze, radio-wave and communications improvement, magnetic compasses and odographs, and ionospheric, hydrographic, and radioactivity studies.

In addition to his scientific work Dr. Fleming found time to edit the *Journal of Terrestrial Magnetism and Atmospheric Electricity* (now the *Journal of Geophysical Research*) from 1932 to 1948, and the *Transactions of the American Geophysical Union* from 1925 to 1947. His duties as General Secretary of the Union during the

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same period included the management of its business affairs.

Many honors came to Dr. Fleming during his lifetime: honorary degrees from
the University of Cincinnati and Dartmouth College, election to the National
Academy of Sciences in 1938, the William Bowie Medal from the American Geophysical
Union in 1941, the Charles Chree medal and prize of the Physical Society of London
in 1945, and the Commander's Cross of the Royal Order of Saint Olav of Norway in
1948.

Dr. George Sarton, a Research Associate of the Institution in the history of science from 1918 until his retirement on September 1, 1949, died on March 22, 1956, in Cambridge, Massachusetts. Born in Ghent, Belgium, August 31, 1884, and educated there at the University of Ghent, Dr. Sarton went to England at the outbreak of World War I and came to the United States in 1915, where he first taught at the University of Illinois and George Washington University, and then became associated with the Institution. While maintaining his connection with the Institution, he joined the staff of Harvard University in 1920, becoming a full professor in 1940.

In his chosen field of the history of science, Dr. Sarton stood pre-eminent.
As an advocate of what he termed "the New Humanism," he studied all aspects of cul-
ture in their relation to the central theme of his interest--the development of
science. His researches traversed the fields of theology, art, linguistics, geog-
raphy, politics, and the technical arts. His writings were prodigious. Under
the aegis of the Institution he wrote a monumental three-volume survey of the
sources in the history of science through the fourteenth century entitled _An Into-
duction to the History of Science_.

Dr. Sarton founded and for many years edited the journal _Isis_, a review of
the history and philosophy of science, and its companion _Osiris_, where substantive
studies in the same fields were published. At the time of his death, Dr. Sarton
was working on a projected eight-volume _History of Science_ from its beginnings to
1900.

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Dr. Earl H. Morris died on June 24, 1956. Except for an early seven years
with the American Museum of Natural History, his scientific career from 1924 to
his retirement on June 30, 1955, was spent entirely with the Division of Histori-
cal Research (now the Department of Archaeology) of the Carnegie Institution.

After leading expeditions to Guatemala, New Mexico, and Arizona, and ex-
ploring the Aztec ruins in New Mexico, he directed the Institution excavations
in Yucatán from 1924 to 1926. His major achievement there was the excavation
and restoration of the Temple of the Warriors at Chichen Itza. After 1929,
Dr. Morris devoted himself exclusively to research in the origin and development
of Southwestern culture, and he became the outstanding authority on Pueblo-
Cliff Dweller architecture. His advice and services were frequently requested
by the U. S. National Park Service in connection with important projects on the
Aztec (New Mexico) and Canyon de Chelly (Arizona) National Monuments and the Mesa
Verde National Park in Colorado.

Dr. Morris possessed an unusual combination of gifts: aesthetic sense
coupled with engineering skill and ingenuity, and a lucid literary style. He
was the author of *The Temple of the Warriors* and of numerous papers in scientific
journals. His signal contribution to Southwestern and Middle American archaeol-
ogy earned the Alfred Vincent Kidder Award of the American Anthropological Associ-
ation for 1953.

Dr. Norman Levi Bowen, who joined the staff of the Geophysical Laboratory
of the Institution in 1910 and retired on June 30, 1952, died at his home in
Washington on September 11, 1956. During his long association with the Labora-
tory--broken in 1919 when he served for a year as Professor of Mineralogy at
Queen's University in Kingston, Ontario, and again (1937-1947) when he was
Distinguished Service Professor of Petrology at the University of Chicago--he
carried on important studies in the phase equilibria of mineral systems at high
temperatures and published the classic monograph *The Evolution of Igneous Rocks*

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(1928). Dr. Bowen was especially noted for his success in bringing chemical knowledge to bear on the problems of geology through new techniques of investigation in the laboratory and the correlation of laboratory findings with field evidence. His outstanding contributions to science were recognized by election to the National Academy of Sciences in 1935 and to membership in the Royal Society of London in 1949. The highest award of the Geological Society of London, the Wollaston Medal, was presented to him in 1950, and in the same year he received the Roebling Medal of the Mineralogical Society of America. In 1953 he was the recipient of the Hayden Memorial Geological Award from the Academy of Natural Sciences of Philadelphia.

Dr. Edison Pettit, who came to the Institution from the Yerkes Observatory in 1920, retired as Astronomer of the Mount Wilson and Palomar Observatories, Pasadena, California, on June 30, 1955, after thirty years of service. Dr. Pettit, in collaboration with Dr. Seth Nicholson, is responsible for the development of sensitive vacuum thermocouples for measuring the heat radiation of celestial bodies. By this means he has obtained fundamental results that are still in use after almost three decades.

Pettit's long and detailed study of nebulae, starting with a 6-inch and ending with the 100-inch telescope, was concerned especially with T Coronae Borealis and Nova Puppis. During the last ten years Dr. Pettit has used photometric methods in measuring the total brightness and colors of some 563 extragalactic nebulae, with results of importance for observational aspects of the apparent expansion of the universe. The scope of Dr. Pettit's work is attested by his numerous articles in the *Publications of the Astronomical Society of the Pacific* and in the *Astro-physical Journal*.

Dr. Jens Clausen, of the Department of Plant Biology, retired on June 30, 1956. He came to the Department from Denmark in 1931 as an investigator in cytology and

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genetics to continue on a broader scale the work of Dr. Harvey Monroe Hall in the field of experimental taxonomy. With the later collaboration of David D. Keck, taxonomist, and William M. Hiesey, physiologist, he conducted a series of long-range field and laboratory experiments on the forces that govern the distribution and evolution of plants under natural conditions. Their detailed findings and general conclusions have been embodied in a series entitled *Experimental Studies on the Nature of Species*, the fourth volume of which is now in press. The series is considered a classic in its field. In 1949 this group of investigators was awarded the Mary Soper Pope Medal of the Cranbrook Institute of Science for distinguished accomplishment in botanical sciences.

Since 1943 Dr. Clausen has also made important contributions to the study of the genetics of various forage grasses in the course of developing strains suitable for planting under the widely different climatic conditions of the nation's great cattle ranges.

In recognition of his contributions in the field of plant biology, Dr. Clausen was elected in 1951 to membership in the Royal Academy of Sciences and Letters of Denmark, and in 1955 he was elected a foreign member of the Royal Swedish Academy of Sciences. In that year, also, he served as vice-president of the Society for the Study of Evolution, and has this year served as its president.

Dr. George Washington Corner retired on June 30, 1956, after serving nearly sixteen years as Director of the Institution's Department of Embryology in Baltimore, Maryland.

Before coming to the Institution Dr. Corner was an assistant professor of anatomy at the University of California (1915-1919), associate professor at the Johns Hopkins University (1919-1923), professor at the University of Rochester (1923-1940), and guest lecturer at the Royal College of Surgeons and the Universities of London, Manchester, and Edinburgh. On leave from the Institution from 1952 to 1953, he occupied the chair of George Eastman Visiting Professor at the

-36-

University of Oxford and was an Honorary Fellow of Balliol College.

Under his direction the Department of Embryology continued the programs mapped out by his predecessors, but gave increasing emphasis to the physiological, chemical, and physical problems of embryology and of mammalian reproduction. For more than forty years Dr. Corner has carried forward classic research in the anatomy and physiology of mammalian and especially of primate reproduction. With Willard Allen, he was responsible for the isolation of the hormone now known as progesterone, which led to major developments in the whole field of endocrinology.

In addition to his many scientific contributions, Dr. Corner has written a number of books, including several in the fields of medical history and sex education, addressed to the general public. He has received very many high honors, including among others the degree of Doctor of Science, *honoris causa*, from Oxford University. He is an Honorary Fellow of the Royal Society of Edinburgh and a Foreign Member of the Royal Society of London. He has recently served as vice-president of the National Academy of Sciences and of the American Philosophical Society.

Dr. Corner's retirement from the Institution brings no diminution of his active work. He is now a staff member of the Rockefeller Institute for Medical Research in New York City, filling two disparate and congenial roles--as historian of the Institute and as active researcher and adviser in the physiology of reproduction.

...... and Gains

A notable addition to the Institution's staff during the year is Dr. James D. Ebert, who succeeded Dr. Corner as director of the Department of Embryology on January 1, 1956.

Dr. Ebert received his Ph.D. at Johns Hopkins University in 1950, and taught for a year at the Massachusetts Institute of Technology. In 1951 he joined the

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faculty of Indiana University, instituting a program of research and advanced teaching in experimental embryology. His principal work has been directed toward an understanding of the mechanism of synthesis and the interaction of tissue-specific proteins in development. Since 1952 he has combined the established methods of experimental embryology with radiobiological techniques in an investigation of the growth-regulating mechanisms of the chick embryo. Under his leadership the Department will continue to pursue its present researches and to make its resources available to visiting investigators in embryology and related areas. Increasing attention, however, will be paid to a study of the basic mechanisms of differentiation, growth, and morphogenesis in the early embryo.

It gives me great pleasure to announce that before his retirement as President of the Institution Dr. Vannevar Bush was informed that he had been made an Officer of the Legion of Honor as a token of the high esteem in which France holds his outstanding achievements in the field of scientific research, by decree of the President.

The following honors have been received by staff members during the year.

Dr. Ira S. Bowen, Director of the Mount Wilson and Palomar Observatories, was elected an Honorary Fellow of the Indian Academy of Sciences when it met in Hyderabad. Dr. J. Eric S. Thompson, staff member of the Department of Archaeology, was awarded the Viking Medal in archaeology. Dr. Robert K. Burns, staff member of the Department of Embryology, was awarded a John Guggenheim Memorial Foundation Fellowship for travel in Europe to observe work in progress in a number of laboratories in the field of experimental control of sex differentiation.