348 
NATURE 
[January 4, 1917. 
nature of a vector is a mystery, although they 
could write out a complete theory of the central 
axis; and to whom numerical calculations of any 
description are as the abomination of desolation. 
In his Lecons the author has provided the student 
with an ample supply of algebraical exercises, and 
to these the volume before us provides a supple- 
ment, the scope of which is indicated by the 
warning: “ Bien entendu, il n’aura jamais de recul 
devant les calculs numériques, sans quoi il vaudrait 
mieux fermer le livre pour toujours et changer de 
carriere.” The chapters are arranged to be 
worked through, pari passu, with corresponding 
sections in the Lecons, so that a wide extent of 
ground is covered in these 120 odd pages. Close 
attention is paid throughout to relative and abso- 
lute errors. Many of the exercises deal with 
problems occurring in railway management, and 
may be novel on this side of the Channel. The 
book will be a useful addition to the library of 
the teacher or examiner. 
(6) Miss Hudson’s monograph on “Ruler and 
Compasses,” which has somehow strayed into this 
group of elementary text-books, takes us on to a 
higher plane. Class-book in its entirety it can 
scarcely be in the schools of to-day, but none the 
less will it find a place on the shelves of the 
teacher who is in search of leading ideas, of the 
follk who in other days would have exhibited their 
taste for geometrical study in the “Palladium,” 
the “Apollonius,” or the “Ladies’” and “ Gentle- 
men’s” Diaries of their time. There must be 
a considerable proportion of those possessed of 
general culture who see something repellent in 
analysis, who find generalities too great a burden 
for their powers of assimilation, and who never- 
theless have a native talent for the elementary 
investigations of pure geometry. Among them 
is, for instance, that small coterie who feel a 
never-failing charm in the elusive mysteries of 
cyclometry. To these it will appeal as well as 
to the mathematical elect, beginning with the 
cream of the schools—who will find Miss Hudson’s 
book uncommonly useful, for example, in pre- 
paring for their “essay paper,” quite apart from 
its intrinsic interest and value—and passing on to 
the trained mathematicians, whose interests have 
been mainly analytical, and who will be glad to 
find within two covers a host of material such as 
that due to Messrs. Richmond, Gérard, Hobson, 
etc. How many of the old stagers have heard of 
an Einheitsdreher, or can state the meaning of 
geometrography? We cannot better describe the 
author’s scheme than in her own words: “The 
connecting link through the book is the idea of 
the whole set of ruler and compass constructions, 
its extent, its limitations, and its divisions.” In 
completeness and in clarity of exposition it ranks 
with a companion volume in the same series, the 
“Projective Geometry” by Prof. Mathews, and, 
though not comparable in scale, we do not think 
that “masterpiete ” is too strong a word to’ apply 
to each. Some day, but not yet, we may forgive 
Miss Hudson for the omission of an index. 
W. J. G. 
NO. 2462, VoL. 98] 
OUR BOOKSHELF, 
First Course in General Sciencg. By Prof. F. D., 
Barber, M. L. Fuller, Prof. J. L. Pricer, and 
Prof. H. W. Adams. Pp. vii+6o07. (New 
York: Henry Holt and Co., 1916.) 
Tuts book is written for the American school — 
child. It opens with the statement that “the 
primary function of first-year general science is 
to give, as far as possible, a rational, orderly, 
scientific understanding of the pupil’s environ- 
ment to the end that he may, to some extent, cor- 
rectly interpret that environment and be master 
of it. It must be justified by its own intrinsic 
value as a training for life’s work.” Setting out 
with this idea, the authors take the various 
phenomena with which the child is likely to be 
confronted, and deal with them in a manner cal- 
culated to arouse his interest. The opening chap- 
ter deals with lighting : with candles, lamps, and 
kerosene; these subjects lead up to evaporation, 
boiling temperature, etc., then to petroleum, gaso-. 
lene, coal gas, and finally to electric lighting. 
In the second chapter the authors pass .on to. 
heating: fires, stoves, combustion and energy, 
chemical compounds, coal, the measurement 
of heat, house-heating and cooking. A _ third 
chapter is devoted to the refrigerator, which 
plays a large part in the domestic economy. 
of the States; this leads on to ammonia, 
the freezing of water, and cold storage, The 
weather is next discussed. The child by this 
time has gathered some general physical ideas 
and he can the more easily grasp the somewhat 
complex problems now presented to him. Meteor- 
ological instruments, weather charts, the seasons, 
climate and its relation to health, are all de- 
scribed. The principles of ventilation are then 
treated at length, followed by an account of dust,_ 
the vacuum cleaner, and the dangerous, because 
dusty, hangings of rooms. 
The authors then deal with a wholly different. 
subject: food. They are concerned more parti- 
cularly with its preparation on both the large 
and the small scale. The next chapter is devoted 
to micro-organisms, and later chapters to soil. 
physics, sewage, and machinery. 
Thus the whole range of a child’s experience 
is fairly well covered. It is difficult to form an 
opinion as to the general suitability of a book of 
this sort: usually one tells children about these 
things, and adapts one’s methods to the audience, 
developing a theme when it seems desirable, but. 
never treating two different audiences in the same 
way. Probably the best use of the book is as a 
teacher’s guide to give him “copy” which he 
can-work up and adapt to. his own class. 
The Mechanical Star-bearing Finder: A Simple 
Guide to Night Marching in Southern England 
and North France. By E. T, Goldsmith... 
(London: George Philip and Son, Ltd.) Price 
55. net. 
TuIs is a convenient pocket arrangement by 
means of which one can solve several of the 
problems which are capable of solution by the 
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