New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1874-04-21

not be initiated in our experiments. Our business |
is to observe the conditions under which certain |
effect is produced. But some of these conditions
may involve a great length OF time. There ars ex-
perments on record which extended over i've or ten
years. and even over large part of lifetime But
such intervals of tune are almost nothing TO the
time during which nature may have been at work.
The contents of a mineral vein in Cornwall may
have been undergoing gradual change for more than
q million of years. All metamorphic rocks have en-
dured high temperature and enormous pressure Tor
inconceivable periods OF time, so that chemical
geology generally is beyond the reach OF experiment.
The author applies this principle to Darwins theory
Of the origin of species 1t has been argued against
il that no clear instance OF the production OF
new species has been discovered during histor-
ical period of perhaps four thousand years. But,
SAYS Professor Jevons, it might as well be argued
that no geological changes are taking place. because
no new mountain has risen in Great Britain wlthin
the memory Of man. Our experience OF geological
changes is mere point in the infinite progression oi
time. When we know that rain water VIII carry
away minute portion Of limestone in solution Dy
falling upon the rock we do not hesitate to multiply
that quantity by millions and millions, ana assert
that in course of time mountain may be dissolved.
The action of physical causes upon the characters OF
animals by natural selection is subject to precisely
the same remark. Nature mas HldOc hO tAPN4'""N
at all for us within historic times. Thus the argu-
ments against Darwin's theory founded on the nom
observation of natural changes within the historical
period. concludes the author, are purely negative,
and of the weakest character:
One of the most interesting portions OF the work is
devoted to the approximate character OF our knowl-
edge of physical laws. Many persons, the author
afirms are msled by the expression exact science,
and think that the true laws OF the universe are
reached with absolute precision by scientific meth
ods There is even an impression that when mathe-
NAUTICAL formulas have been applied TO branch OK
science, this portion OF knowledge assumes new
name and admits Of higher mode of reasoning
than those sciences which are not mathematical.
The degree of accuracy obtained in the science OF
astronomy gives certain plausibility to erroneous
notions of this kind. Many persons, no doubt, be-
eve that it is proved that planets move in elpses,
and that all Keplers laws hold exactly true. But,
maintains the professor there double error in any
such notions. First Keplers laws are not proved II
by proof mean certain demonstration OF their
exact truth. Second, even assuming Keplers laws
TO be exactly true in theoretical point OF view, the
nlanets never move according TO those laws. Even
if we could observe the motions of planet OF per-
fectly globular form, free from all pertmbing or
retarding forces, we could never perfectly prove
that it moved in an elipse In order to do this we
should have to infinitely small angles, ana
infinitely small fractions of second. We should
have to perform impossibilites We can only show
that the motion of planet approaches very nearly
to the form of an epse. But if we assert that the
form is an ellipse we go beyond our data and make
an assumption which may be more or less probable,
but which cannot be proved in the strict sense OF
that term. As matter Of fact, no planet does move
in perfect ellipse manifest the truth OF kepers
laws exactly. Nothing is certain in scientific
method than that approximate coincidence is alone
possible ,,,
In truth men can never solve problems fulfilling
the complex circumstances of nature. All laws are
in certain sense hypothetical, and apply exactly
to nothing which we can know to exist. IN place of
the actual objects which we see and feel the math-
ematician invariably substitutes imaginary objects
When we probe the matter to the bottom, physical
astronomy is as hypothetical as Euclids elements.
There may exist in nature perfect geometnoal hg-
ures, but to science il is matter OF indifference
whether they do exist or not, because in any case
they must be beyond our powers OF appreciation.
If we submitted perfect circle to the most rigorous
measurement, we could never discover whether ii
were perfect or not. Still in geometry we argue con-
corning perfect squares and circles and the conclu-
sons apply to existing objects far can besure
that they agree with the hypothetical condition Of
our reasoning. But III reality this is all that we eau
do in the most perfect of the sciences OF Nature.
In astronomy no doubt we meet with the nearest
approximations TO actual conditions. The law OF
gravity we believe to be exactly true but in no one
case can we calculate its accurate results. The law
asserts that every particle of matter in the universe
attracts every other particle. Hence we cannot
know the force acting on any one particle unless we
know the masses and positions OF all the other par
tcles in the universe The physical astronomer has
from the first made the sweeping assumption that
H. 6
bic perturbing effects our planetary system.
Thus the problem becomes at once hypothetical, be-
cause there is little doubt that graytation between
our sun and planets and other systems must exist i'll
some degree. Still further, when astronomers con-
slider the relations of planetary bodies among
themselves, all their processes grossly approx
native. They assume that each of the planets is
perfect ellipsoid with smooth surface and no.
mogeneous interior. But this assumption is alto
gether untrue. Ii is cOntradcted by every noun
tam and valley, every sea, every mine, every
grain Of sand. The calculations of the astTcn-
omer cannot be made perfect unless he takes into
account the Himalayas and the Andes the Atlantic
and Pacific, nay every hill, and every ant-hill.
But so far from having yet considered any local IL
equality of the surface they have not yet decided
upon the general form of the earth. 1t is yet mat
ter of speculation whether or not the earth is an
ellpsoid with three unequal axes. Bat if we can
not accurately learn the form of the planet on
which we live, how can we determine that OF the
remote members Of the solar sytemi
The same general statements arc still more evil
IDENTIFY true of the other branches of physical SCI
ence. We speak of inAexible bars, inextensible
lines, heavy points, homogeneous substances, uni
form spheres, perfect fluids and gases, from which
we deduce an infnty of beautiful theorems. But all
is hypothetical. There is such thing as an in
a.. hnr Ntnr No linz IL H.