DrcemBER 6, 1906 | 
NATURE 
tion in general, and lastly the Sensus Communis, and 
its method is under each head to give as consistent a 
view as possible of what was severally taught by 
Alemaeon, Empedocles, Democritus, Anaxagoras, 
Diogenes of Apollonia, Plato, and Aristotle. There is 
little or no attempt to criticise these writers from the 
standpoint of modern philosophy. But the statement 
is very clear, the discussion of disputed points scholarly, 
the facts are well arranged, and the literature—to judge 
from the footnotes and the list of books consulted— 
seems to have been thoroughly studied; although one 
misses a reference to one recent work on the ‘‘ De 
Anima ’’—that of Rodier, whose commentary, if not 
his translation, has been regarded by competent judges 
as indispensable. 
As dissection was practised as early as Alemaecon— 
he is stated to have been a pioneer in this direction— 
there is perhaps room for our wonder that the Greeks 
did not in their swift way attain some more consistent 
and conclusive theory regarding the working of the 
senses and the nervous system as a whole. Possibly 
they were encumbered with the armour of pre-supposi- 
tions with which they went forth to encounter nature— 
Empedocles and Anaxagoras with their respective doc- 
trines that like is perceived by like, and contrary by 
contrary; Aristotle with his antitheses of form and 
matter, of dynamis and energeia; nearly all of them 
with a disposition—to which Aristotle, worse advised 
than Plato, succumbed—to regard the heart and not 
the brain as the physical centre of the intellectual life. 
But at the same time one notes in this volume how little 
right we have to throw stones at them; e.g. how 
modern physics (to quote Prof. Beare’s words) ‘is as 
helpless to explain colour as physiology to explain 
olfactory function,’’ or, again, that ‘‘ the psychology 
of taste has advanced little beyond the popular and 
superficial stage at which Alcmaeon left it.’’ Still, 
when all is taken into account, the final impression is 
one of admiration for the insight—which is genius— 
of an Aristotle, e.g. when ‘‘ he rejected as if by antici- 
pation the Newtonian emission theory of light ’’; for 
the skill, too, with which he could produce a theory 
that would do justice to all the valuable elements in 
earlier philosophy, e.g. when he harmonised Em- 
pedocles and Anaxagoras by his statement that per- 
ception is a relation in which what was unlike becomes 
like. 
The occasional inconsistencies in Aristotle—those 
spots in the intellectual sun—are well discussed by our 
author. Aristotle’s views, or possible views, on 
biological development have always been a difficult, if 
interesting, subject, for in one passage of the ‘“‘ De 
Sensu’’ the master rejects Democritus’s account that 
each of the other senses is ‘fa kind of touch’’; but 
while Dr. Ogle, on the ground of that passage, hesi- 
tates to credit Aristotle with the belief ‘“‘ that the 
remaining special senses are but modifications of touch 
or general sensibility,’’ Prof. Beare, on the other 
hand, finds it ‘“‘ hard to suppose that Aristotle—the 
pioneer, in general terms, of the theory of evolution 
not only physical but physiological and psychological 
—should in this particular application of his theory 
have failed to recognise it, or have denied its truth 
NO. 1936, VOL. 75| 
simply because it was a doctrine of Democritus.’’ On 
every account this volume is to be commended to those 
interested in the development of theories of sense-per- 
ception. 
GRAVITATIONAL ASTRONOMY. 
The Collected Mathematical Works of G. W. Hill. 
Vols. ii., ii. Vol. ii., pp. v+339; vol. iii., pp. 577- 
(The Carnegie Institution of Washington, 1906.) 
HE second and third volumes of Hill’s works carry 
to 1890 the republication of his papers prepared 
for the American ephemeris and his miscellaneous 
writings. The latter volume, which is entirely devoted 
to the theory of Jupiter and Saturn, is probably without 
parallel as a piece of calculation. It is a splendid and 
enduring monument to ten years’ incessant labour, and 
the nicety of agreement of its predictions with observ- 
ation continues to justify the pains spent upon it. It 
replaced Leverrier’s theory, which was published while 
this was in course of production, and Hill found him- 
self unable to point to any definite omission or flaw in 
Leverrier’s theory which would account for the much 
inferior accuracy of its results; it seems to be due to 
accumulation of almost impalpable differences, and if 
some of Hill’s work strikes one as over-elaborated, one 
can always look to the ‘‘ Theory of Jupiter and 
Saturn ’’ for justification. 
At the same time, one cannot help feeling in turning 
over some of these papers that to an adept  straight- 
forward calculation becomes an end in itself. The 
memoir, No. 48, on the lunar inequalities due to the 
spheroidal figure of the earth is an example. This is 
entitled also a supplement to Delaunay’s theory of the 
moon. The theoretical additions are fairly obvious, 
and the main part of 143 pages is occupied with the 
steps required for determining 165 terms in the moon’s 
longitude and 209 in latitude which are factored by 
the earth’s ellipticity. Not the fiftieth part of these 
terms reaches o’.1 in amplitude, and not the tenth of 
o’.o1r. Most people will regard this as more striking 
in its proof of the author’s colossal patience than in 
any other quality. 
Probably no writer of the same originality has been 
content to follow his predecessors’ models, upon occa- 
sion, so closely as Hill. They owe him much. The 
paper referred to above is the most elaborate applica- 
tion of Delaunay’s method outside Delaunay’s own 
work. Hill’s ‘‘ Jupiter and Saturn ”’ is the greatest 
monument in existence to the power of Hansen’s 
methods, Hansen’s own Lunar Theory not excepted. 
It was to the problem of these two great planets that 
Hansen first made serious application of his methods 
in 1831. But, as Hill puts it, he “‘ seems to have been 
carried away by the ambition of applying his method 
of treatment to the lunar theory,’’ and never returned 
to it. If anyone would disabuse his mind of the com- 
mon misapprehension that Hansen’s ideas are uncouth 
and his methods formless, and gain at the same time 
a concrete view of Hansen’s method, he could not do 
better than follow out the steps of the Auseinander- 
setzung as applied by Hill. Hill’s modifications, few 
though important, are no obstacle. The truth be- 
