May 6, 1915 | 
NATURE 
257 

support of a healthy community life. Even if the 
American farmer is indifferent to the appeal for 
better surroundings as set forth in these pages, 
many of the problems discussed demand con- 
sideration on account of their economic import- 
ance. In the matter of roads, for instance, only 
8 to 9 per cent. of the total roads of the States 
have been improved by surfacing with gravel, 
oyster shells, etc., whilst the remainder are often 
so despicably bad that the cost of haulage of 
farm products is three to four times the legitimate 
amount. The one-street town is passing ‘away, 
and many of the suggestions advanced by Mr. 
Waugh as to farm and town planning are well 
worthy of practical adoption. 


TEXT-BOOKS OF PHYSICS. 
(1) Cours de Physique. By Prof. E. Rothé. 
Pp. vi+183. (Paris: Gauthier-Villars et Cie, 
1914.) Price 6.50 francs. 
(2) Traité de Physique. By Prof. O. D. Chwol- 
son. Translated by E. Davaux. Pp. vi+266. 
(Paris: A Hermann et Fils, 1914.) Price 9 
francs. 
(3) Preliminary Practical Science. Some Funda- 
mental Principles of Physical Science, with their 
Practical Applications. By H. Stanley. Pp. 
vili+128. (London: Methuen and Co., Ltd., 
n.d.) ‘Price rs. 6d. 
(4) Outlines of Applied Physics. By H. Stanley. 
Pp. vili+227. (London: Mills and Boon, Ltd., 
1914.) ‘Price 25. 6d. 
45) Preliminary. Practical PLN SiG Ser meteart seit. —— 
Heat. By-A.,.E. hyster: —Pp. wii+73. :(Dub- 
lin: Educational Co. of Ireland, ro14.) — Price 
maya. neta 
(6) A School Electricity. By C. J. L. Wagstaff. 
Pp. xi+250. (Cambridge: At the University 
Press, 1914.) Price 5s. net. 
(7) Elementary Geometrical Optics. By A. S. 
Ramsey. Pp. xi+173. (London: G. Bell and 
Sons, Ltd., 1914.) Price 6s. 
(1) S judged by the size of the first two books 
of the ‘Cours de Physique,” which 
Prof. Rothe is writing, the whole work will be of 
very considerable magnitude. According to the 
author’s foreword, these two books represent 
the introduction only to the course itself, which is 
intended for students who have already studied 
physics, and priniarily for those who are proceed- 
ing to technical institutes. In several ways this 
introduction is rather remarkable. The subjects 
covered in the first book are (i) units, and their 
transformation from one system to another; (ii) 
the principle of similitude in physics; and (iii) 
methods of measuring the fundamental physical 
quantities, and the errors involved. In the second 
NO. 2375, VOL. 95] 
book, the statics of fluids and the experimental 
measurement of densities and pressures are dealt 
with. There is, perhaps, too little stress laid 
upon theory, but there can be no doubt that the 
detailed descriptions of the methods of measure- 
ment with great precision, together with the dia- 
grams illustrating these methods, are in every way 
excellent. 
(2) Many physicists regard Prof. Chwolson’s 
treatise on physics as the best in existence—and 
with justice. Prof. Chwolson has not only given 
us a most complete and accurate survey of ex- 
perimental physics in practically all its branches, 
together with an exhaustive bibliography, but he 
has also contrived to make his work a critical 
essay. The translation of this work into French, 
making it—as it will do—available to those 
students who do not know Russian and read Ger- 
man with difficulty, is a most desirable event. 
That now published is the tenth part, and con- 
tains the chapters on electromagnetic induction, 
Maxwell’s theory, the basis of electronic theory, 
and the principle of relativity. The translation 
has the advantage of having by 
the auther himself, who has, at the same time, 
considerably augmented the edition. The chapters 
on the theories of electrons and relativity have, 
consequently, an added interest, and it will be 
found that they give a very comprehensive survey 
of these subjects which are at present so much 
been revised 
under discussion. 
(3) This little volume adds the 
already large number of similar books which have 
been published within recent years, and follows 
much the same lines of treatment. A consider- 
able number of simple physical experiments are 
described, principally in mechanics, heat and light, 
another to 
fhose in electricity and magnetism numbering 
only half-a-dozen. Each «exercise 
simple statement of the theory of the experiment 
and a description of the method of procedure. 
In some of them, however, the results obtained 
would not be what the student is led to expect. 
For example, in the experiment on the spectrum, 
no lens is used to focus the light on the screen, 
and we are told incidentally that the spectrum 
consists of seven colours. <A refreshing feature 
of the book, however, consists of some excellent 
notes on experimental work which, if all students 
would follow, would bring about a great improve- 
ment in their practical records. 
(4) In the main, this book is a series of ex- 
amples in theoretical physics, for not only are 
there numerous numerical exercises at the end 
of each chapter, but more than four hundred of 
a miscellaneous character at the end of the book. 
| The work, as the author himself points out, is 
combines a 

