258 
in no way descriptive, and therefore could. not 
serve as a text-book. Indeed, it seems rather 
to partake of the “cramming” nature, and would 
tend to make physics appear to consist of a series 
of mathematical formule. Still, provided that it 
does not lead students to neglect the experimental 
side of physics, the book will probably be found 
quite useful. 
(5) This is a little paper-covered pamphlet con- 
taining descriptions of some forty simple experi- 
ments in heat, and, although small, is well printed 
and arranged. The diagrams all represent 
sections of the apparatus, and are free from 
elaborate details. This is a good feature, for, as 
the author points out, it will encourage the reader 
to do the same in his practical records, instead 
of wasting time over sketching the exact appa- 
ratus—a thing which but few students can do 
well. 
(6) It is not often that there appears a physical 
text-book so generally good as this one of Mr. 
Wagstaff. It is the outcome of the author having 
been persuaded to publish a book comprising the 
notes of his lectures at Oundle School, and he 
is to be congratulated on the result. Not only 
is the treatment obviously based upon experience 
in teaching the subject, but the descriptive work 
and the methods of explaining those parts of the 
theory which present difficulties to the average 
student have an originality which is very refresh- 
ing. Besides this, all the diagrams and plates 
are excellent, and these features, together with 
the good printing of the text, give the book a 
general appearance which is very pleasing. One 
or two criticisms may be made. These, however, 
detract but little from the value of the book. The 
first is with reference to the definition of the 
ampere in terms of silver deposited during  elec- 
trolysis. One knows, of course, that it is so 
defined by law, but it cannot be clear to a student 
why the special amount, ooo1118 gram _ per 
second, is chosen. In fact, we disagree entirely 
with the position which the author advocates in 
his preface, viz., that it is desirable to begin 
teaching current electricity using direct reading 
instruments such as ammeters, instead of by 
means of the tangent galvanometer, which, be- 
sides having a mode of action which is simpler 
than that of an ammeter, serves also to measure 
the current absolutely. 
In the second place, the study of electrostatics 
and magnetism ought to be taken earlier than it 
is in this book. The book opens with a very short 
chapter on magnetism, then proceeds with current 
electricity, and the treatment proper of magnet- 
ism and statical electricity is not reached until 
half-way through. It would, however, be possible 
NO. 2375, VOL. 95] 
NATURE 

[May 6, 1915 

for these chapters to be read first, and the objec- 
tion would thereby be partially removed. In any 
case, it is not of great importance, and the book 
is to be thoroughly recomimended. 
(7) This book, also, is well produced, and deals. 
with a subject somewhat neglected. Although the 
treatment is not advanced, it comprises a wide 
field, including the important subjects of achro- 
matism, thick lenses, and optical instruments. 
There are frequent examples which will, no doubt, 
be useful for training the students. It is quite 
certain that there has been for some time an 
opening for a book of this kind, and the present 
volume is well fitted to supply the demand which 
exists. In fact, students of the subject of light 
would be well advised to read this volume in con- 
junction with their text-books of physical optics; 
and those who intend becoming optical instrument 
makers would benefit greatly by studying it. 

OUR BOOKSHELF. 
(idema and Nephritis: a Critical, Experimental, 
and Clinical Study of the Physiology and Patho- 
logy of Water Absorption in the Living Organ- 
ism. By Prof. M. H. Fischer. Second edition. 
Pp. x+695. (New York: J. Wiley and Sons, 
Inc. ; London: Chapman and Hall, Ltd., 1915.) 
Price 21s. net. 
Tuis is the second edition of a work which has 
already attracted some attention in the physio- 
logical world. The author’s main theme is that 
dropsy is not due to disorders of the circula- 
tion, or to changes in osmotic processes, 
but is wholly produced by the tissues them- 
selves sucking up water from the blood, and 
that increase in acidity of the tissues is the 
sole factor in their being able to attract more 
water into their colloid structure. The main 
experiments upon which this theory depends were 
performed by placing dead frogs’ legs and pieces 
of gelatin in fluids of different composition and 
reaction. Even the swelling which occurs in a 
limb when reflux of blood from it is prevented 
by occluding the veins is explained on the acid 
theory. Addition of such salts as sodium chloride 
to the experimental fluid lessens the amount of 
swelling; yet it is well known that excess of such 
salts favours dropsy during life. This is ingeni- 
ously explained by saying that the excess of salt 
lessens vital oxidative processes, and this leads to 
formation of acid, and therefore indirectly to 
cedema. The only piece of evidence advanced in 
favour of this view is that rabbits on an excessive 
salt diet become cyanotic; an impartial. observer 
might quite reasonably argue that cyanosis may 
be the result of the dropsy. 
Prof. Fischer argues that disturbances of the 
circulation cannot be the cause of dropsy because 
in his dead frogs or strips of gelatin, no 
circulation was going on at all, and yet they 
became dropsical. Acidity may be, and probably 
is, one cause in cedema-production; but this is a 


