The sun. [volume] (New York [N.Y.]) 1833-1916, 1906-11-28

completeness Of the combustion.
Prof. Richards also read a paper by him
self and George s. Forbes on the atomic
weights OF nitrogen m silver.
The above were the papers OF Tuesday
morning, November %. The afternoon
until dark was given up 10 a Conversations,
in imitation Of the reunions OF the Royal
Society in London that are called by that
name. It was the first that the Academy
has held and was highly successful, be-
cause 1t afforded opportunities for explana-
tons that one cannot well ask forina public
meeting. Most Of the exhibits, however,
including the best OF them. we're Of appar-
atus, specimens, &C, that well informed
persons had seen before. The best OF all,
m the most perfectly presented, was the
exhibition OF stellar photographs from
the Harvard College Observatory. But
everybody who takes any really deep In
terest in astronomy has seen all that much
more fully and has read the publications
OF the observatory describing them. An
ingenious thing was Prof. Cannon's foetrope
showing the progress OF food through the
slimentary canal OF a fowl, viewed by
X-rays, with the movements Of the stomach
and intestines. There were about fifty
exhibits, again an excessive number.
Wednesday morning was devoted to the
business meeting Of the academyi which
is not open to the public. The papers OF
the afternoon, with the exception OF the
first and last, were astronomical. The
first, by Gilbert N. Lewis, related to the
energy set free in oxidation W. II. Pick
ering illustrated with a gyroscope, which
he held in his hand, the theory which
was advocated, II we remember rightly,
by George Darwin in his lectures on
tides: that all the planets except Neptune
and to some extent Uranus also, have
turned topsy turvy since they first became
independent bodies. As long az IN parts
Of a planet were not rigidly connected
Kepler's third law would make the side
Of the planet nearer the sun have a greater
velocity han the further side. In other
words the rotation on its axis must have
taken place in the opposite direction to
its revolution around the sun, which agrees
with the present mode Of rotation OF Nep-
tune but Is the opposite to the present
direction Of rotation OF the earth, Mars,
Jupiter and Saturn and presumably also
Of Mercury and Venus the observations
Of which are open to doubt. Indeed, the
original rotation would have been retro
grade, or N~eptunelike, whatever hi law
OF attraction were, as long as the planets
were attracted to the centre OF the sys-
tenn; that il, as long as they performed
anv revolution around the centre. But the
tides tend to cause a retardation OF the
rotation OF the planet on its axis, and this,
upon the principle OF the gyroscope, tends
to cause the planet gradually to be upset.
In the case Of Uranus, this upsetting has
been apparently half performed, so that
the axis OF that planet is nearly in the plane
Of it's orbit. There certainly are tides on
that planet, and these must be slowly acting
to tip it over into h position OF the inner
planets.
Mr.. Pickering illustrated the matter by a
pyroscope upon whose rotation he could
bring to bear a greater or less friction at
will. The remainder OF the paper, which
was more original, related to the ninth and
tenth satellites Of Saturn, both OF which
were discovered by Mr.. Pickering himself
by the aid Of photography. The ninth.
which is the outermost Of all and conse-
auently may be presumed to have beer
separated from the planet at an extremely
early date, has a retrograde motion around
Saturn, Indicating, as il would seem, that
the planet had a retrogade rotation ON its
axis at the time that satellite was separated
from it. The tenth satellite lin the order of
discovery lies in the narrow annular space
between the orbits of two satellites both
much larger than il. The very curious cir
cumstance about it is that when it was first
discovered it was moving in a peculiar orbit
greatly inclined to the planes Of the other
satellites. Then Saturn, owing to the earth's
--.z a.,-uo naaaaI koA vaar kba Itrac%f1-
Of the sun to be observed; and when next
this satellite could be seen it was moving
IN an entirely different orbit and was behav-
ing like any common satellite. Mr.. Picker
ing has succeeded in proving that in the
interval it was at one time very close to the
large satellite Titan. whose orbit lies next
within that Of the tenth satellite; so hat
it is probable that it was drawn into its
present orbit by the attraction Of Titan.
One wonders what it will do next.
8. I. Bailey, who is well known to the
astronomical world for his skilful use
OF the Bruce photographing telescope,
described the performance OF that instru-
ment. The whole heavens, north and
south, lave already been covered by 1900
plates, which are estimated to show 5000, 900
stars In all. Another set is now being
made with exposures OF -FOUR hours, show
ing stars down to the eighteenth magni-
tude; and this will show some 80, OOO, 900
stars. As one indication Of the value OF
the work of this instrument Mr.. Bailey
mentioned thai when the instrument was
first set up the total number OF stars known
TO be variable was about two hundred, but
the study OF the 1900 plates, though as
yet it is very far from complete, has added
more than 1000 new variables. These large
numbers enable astronomers TO study the
system of the visible heavens statistically;
and it is only by statistical studies that
its true structure can ever be made out.
This was illustrated by the next paper,
which was by Prof. George c.. Comstock,
the director OF the Washburn Observatory
in Madison, Wis. This observatory, created
by Watson and greatly improved bv Holden,
has a particularly fine meridian circle and a
clock perhaps never surpassed.
Prof. Comstock, who has the typical
astronomical physiognomy, and especially
that sharp eye of the Alvan Clark type,
has been redetermining the places of stars
of the seventh and eighth m~agnitudes
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