OCTOBER 29, 1897. ] 
descended from both of them; or, if not, our 
descendants (should we have them) will be. 
Genealogies are not, as Professor Brooks 
states, ‘represented by a slender thread of very 
few strands,’ but by the branching tree to 
which he objects, except that there are many 
trees whose branches interlace and anastomose. 
J. McKEEN CATTELL. 
CoLUMBIA UNIVERSITY. 
SCIENTIFIC LITERATURE. 
RECENT BOOKS ON PHYSICS. 
Modes of Motion. By A. E. DoLBEAR. Boston, 
Mass., Lee & Shepard. 12mo. 120 pp. 
The second title of Professor Dolbear’s little 
book is ‘Mechanical Conceptions of Physical 
Phenomena.’ It is essentially a popular pres- 
entation of the fundamental properties of 
matter as contrasted with those which the au- 
thor assumes the ether to possess. Matter is 
contrasted with ether in reference to a series of 
twenty-two of its commonly recognized attri- 
butes, in none of which are the two found iden- 
tical, and in the great majority of cases they 
are declared to be directly opposed to each 
other. Indeed the author makes special effort 
to demonstrate the absolute dissimilarity of 
matter and ether, and in so doing even goes so 
far as to declare that the latter in no way af- 
fects the senses. But he evidently believes in 
the possibility of transforming ether into matter 
and matter into ether and the indestructibil- 
ity of matter or the impossibility of trans- 
mitting the elements he regards as tentative 
assumptions. A fewsentences are devoted toa 
consideration of the origin of the ether itself, 
but the author finds quick refuge in the easy 
“assumption that it was in some way and at 
some time created,’ this being, he declares, more 
rational than to assume that it always existed. 
The book will be found readable and interesting 
by students of physical science. 
Deductive Physics. By FREDERICK J. RoGERs, 
M.S. Ithaca, New York, Andrews & Church. 
8vo. 250 pp. 
This book deserves consideration by all who 
are seeking a satisfactory college text-book of 
physics. It isin many respects different from 
any of the almost innumerable candidates for 
this distinction that have appeared during the 
SCIENCE. 
669 
past decade. Of these nearly every one has its 
merits and all have faults, but the variety is so 
great that the special necessities of almost 
every situation can be satisfied. There has 
been, however, a regrettable tendency in two 
directions. On the one hand, there have ap- 
peared several treatises very complete, very 
well prepared, but so large as to be really 
formidable and quite impossible of mastery in 
the time usually allotted to this subject in the 
college curriculum. The use of these com- 
pelled the adoption of the plan of omitting or 
‘skipping’ many pages or even chapters, which 
is by no means to be commended under all cir- 
cumstances. On the other hand, many college 
text-books are offered in which laboratory exer- 
cises are made so prominent as to seriously 
interfere with and often absolutely prevent a 
proper appreciation of the ‘theory of physics.’ 
Within afew years afew books have made 
their appearance in which both of these evils 
have been largely avoided and in which it has 
been attempted, as in the volume under con- 
sideration, ‘to present, in compact though 
logically complete form, the principal facts, 
laws, definitions and formulas of the science of 
physics.’ In the present instance the author 
has enjoyed a large measure of success. His 
definitions of fundamental terms and principles 
are, in the main, sound and discriminating. 
Although the discussions are generally concise, 
they are generally satisfactory, and no impor- 
tant phase of the subject has been entirely 
omitted. The illustrations are diagrammatic 
and clear and the leading propositions are 
illustrated and enforced by well-selected prob- 
lems. No attention is given to experimental 
or laboratory exercises, but it is assumed that 
these accompany the use of the book whenever 
possible. In the opinion of the writer the 
author has made a mistake, unfortunately not 
an extremely uncommon one, in introducing 
several unauthorized and not generally recog- 
nized names for derived units, such as kin, 
gramkin, spoud, etc. This tendency towards 
multiplication of unit names has little to com- 
mend it and there is serious objection to it. It 
was the unanimous decision of the Chamber of 
Delegates of the International Electric Con- 
gress of 1893 that in electricity and magnetism 
