235 
MaALURE 
[Aprit 8, 1897 
mental facts appear nearly inexplicable in the actual 
state of this theory; nevertheless, if we had only the 
“ Réflexions ” to guide us, we should have to regard him 
as an adherent of the caloric hypothesis. Carnot died 
of cholera in 1832, and some forty years elapsed before 
the publication of his note-book showed how his views had 
changed since 1824. We have only space for one extract. 
“On peut donc poser en thése générale que la puissance 
motrice est en quantité invariable dans la nature, qu'elle 
nest jamais, & proprement parler, ni produite, ni detruite. 
A la vérité, elle change de forme, c’est-a-dire qu'elle 
produit tantét un genre de mouvement, tantot un autre ; 
mais elle n’est jamais anéantie.” 
Then follows an estimate of the number of units of 
heat required for “la production d’une unité de puissance 
motrice”! One cannot help wondering what might have 
happened if he had lived a few years longer, or if his 
views had not remained so long hidden. 
As it is, the subsequent development of thermo- 
dynamics has not been the work of one person or of 
one country. The chapters in which Prof. Mach traces 
its growth, are amongst the most interesting in the book. 
One of his titles—‘ Das Mayer-Joule’sche Princip ”— 
recalls a controversy the echoes of which have not yet 
died away, and indicates his position with reference to 
it. That position is one which many of our countrymen 
will not willingly accept; any more than they would 
accept the statement made on p. 261—“Im Grunde ist 
der Weg, auf dem Joule zu seiner Entdeckung gelangt, 
sehr ahnlich demjenigen Mayers.” But it would be 
unfair to allow such brief quotations to lead to the 
inference that the author is unfair or influenced by 
national bias. On the same page he draws attention to 
the soundness of Joule’s scientific method ; points out 
that he never befogged himself with metaphysical con- 
siderations ; and that his theories were always based 
upon or controlled by experiment. Nor can we justly 
apportion the credit due to Mayer without considering 
the circumstances under which he thought and wrote, or 
without realising how imperfect (see his correspondence 
with Bauer and Griesinger) was his knowledge of physics. 
In the technical skill, the clearness and completeness of 
Helmholtz’s paper ‘‘ Ueber die Erhaltung der Kraft,” we 
have a complete contrast to Mayer's writings. After an 
account of the progress which thermodynamics owes to 
the researches of Clausius and Lord Kelvin, we have the 
following comparison of the manner in which they pre- 
sented their investigations to the world. 
“Tn his exposition, Thomson is always quite frank 
and straightforward in dealing with the difficulties which 
meet him, the course that he strikes out is always the 
shortest and simplest, his methods are perfectly clear, 
and the motives which guide him in his investigations 
are visible to every one. In Clausius’s exposition, there 
is always a touch of ceremony and reserve. Often 
one scarcely knows whether Clausius is more concerned 
to make a statement or to suppress it. The principles 
of the subject, instead of being deduced from simple 
experiences, are built up on specially assumed funda- 
mental propositions ; these look as though they were 
nore reliable, but do not really offer any greater security 
than the experiences which might have replaced them. 
He has, too, a predilection for creating new names and 
ideas, which are not always necessary. But none of 
these personal and unessential peculiarities can mar the 
respect which we feel for Clausius’s work.” 
NO. 1432, VOL. 55 | 
Further chapters are devoted to the principal pro- 
positions in thermodynamics, the absolute scale of 
temperature, the principle of energy, and the relation 
between physical and chemical progress. 
Up to this point we have nothing but praise for Prof. 
Mach’s treatise: it will do much to revive interest in a 
subject which has suffered temporary eclipse by the 
larger developments in recent times of electrical science. 
The style is clear and forcible, and a due sense of pro- 
portion is shown in the arrangement of the subject- 
matter. We admire his mathematical skill, his critical 
insight, and the fairness with which he endeavours to 
apportion praise. The student will find him a trust- 
worthy guide, and the teacher will recognise the frank- 
ness of a colleague who knows where the difficulties are 
and does not slur them over. 
To some the remainder of the book will be of equal 
interest, as it undoubtedly is original, and after the 
author’s own heart. But the reader who has bargained 
only for a historical and critical exposition of the prin- 
ciples of heat and thermodynamics, may be excused for 
feeling that he has been betrayed. For in the last twelve 
chapters Prof. Mach takes the bit between his teeth, and 
roams at will over the domains of scientific thought, 
philosophy, psychology, the theory of cognition, language, 
esthetics, metaphysics and mysticism. To say that there 
is a ‘manifest solution of continuity” between these and 
| what precedes, would be incorrect ; but the choice and 
arrangement of subjects is somewhat kaleidoscopic and 
bewildering. In the absence of any index, reference is 
difficult (though here we may be confusing cause and 
effect). When we want to refer to an ingenious sugges- 
tion for inducing sparrows to progress by running instead 
of hopping, we find it in a footnote to a chapter on 
“Die Sprache” ; while an interesting observation on the 
suckling and weaning of children finds place in a foot- 
note’to a chapter on “ Der Begriff.” This term (Begriff) 
is defined in a previous chapter on “ Die Vergleichung 
als wissenschaftliches Princip,” in which the author also 
discusses the question, Was zs¢ eine theoretische Idee? 
Perhaps the most highly variegated chapter is that on 
“ Der Sinn fiir das Wunderbare.” 
The proofs of the book have not been carefully read. 
There are misprints in the German text, and still more 
in the English quotations and references. The diagrams 
are numerous and clear, but the half-dozen full-page 
illustrations are not a great success. Joule is represented 
by a coarse reproduction of Jeens’ engraving. The 
portrait of Clausius seems to be the best. That of Lord 
Kelvin is the worst ; at any rate, it is as bad as it well 
could be. pu. 
CELL-STRUCTURE AND REPRODUCTION. 
The Cell in Development and Inheritance. By Edmund 
B. Wilson, Ph.D., Professor of Invertebrate Zoology, 
Columbia University. (Columbia University Bio- 
logical Series IV.) Pp. xvi. 371. (New York: The 
Macmillan Company. London: Macmillan and Co., 
Ltd., 1896.) 
RIGINALLY produced as the substance of a series. 
of lectures of a popular character upon the problems 
| of individual development and inheritance, the book 
