Juty 18, 1912] 
NATURE 501 
be ploughed into the soil, and he carefully returns 
to the land all the produce of the crops that he 
can. The first process causes the addition to the 
soil of complex carbohydrate material, cellulose, 
starch, &c., and of protein synthesised by the plant 
during its growth; these substances make good 
the loss of carbon and, in some instances, of nitro- 
gen also, and they further supply stores of energy 
for the numerous organisms of the soil. The second 
process involves the collection of animal and human 
excreta, which are returned to the land under the 
most favourable conditions. Finally, the crop on 
the land is allowed:,apperfectly free field and no 
competition is tolerated ; weeds are rigorously kept 
down, and the most careful tillage obtains. 
We need not go into a detailed consideration 
the actual methods, but it comes as a shock 
read that practices we thought were initiated in 
cur times have long been common among the 
Chinese. No one can read the book without being 
struck by the immense patience and industry of the 
peasants and the remarkable way in which they 
have reached the same principles of cultivation as 
the Western farmer. The book can be cordially 
recommended to the student of agriculture, who 
cannot fail to be charmed with the farmers and 
labourers depicted in its pages. 
of 
to 
OUR BOOKSHELF. 
The Heat Treatment of Tool Steel: an Illustrated 
Description of the Physical Changes and Pro- 
perties Induced in Tool Steel by Heating and 
Cooling Operations. By Harry Brearley. Pp. 
xvii+160. (London: Longmans, Green and 
Co., 1911.) Price ros. 6d. net. 
Tue subject of the heat treatment of steel is 
one which during recent years has_ received 
a large amount of attention, and the results 
of numerous researches in England, on the Con- 
tinent, and in America have been published before 
various technical societies. These have, how- 
ever, for the most part dealt with special branches 
of the subject, largely from the theoretical point of 
view, and comparatively little has been published 
by men who have had to deal with the application 
of the various theories in their daily practice. 
This little treatise, while avoiding the more 
abstruse theories, brings together in a collected 
form a great deal of practical information on this 
important subject, which cannot fail to be of great 
use both to the practical man and also to those 
engaged in scientific research. The author, while 
avoiding any detailed discussion of the various 
theories of hardening and tempering, has con- 
cisely and clearly, if very briefly, explained the 
phenomenon of recalescence, and the influence of 
heat-treatment on the structure of steel is illus- 
trated by some excellent photomicrographs. 
The chapter on the hardening of typical tools 
and the special methods of treatment essential to 
obtain satisfactory results is illustrated by 
NO. 2229, voL. 89] 
| nutrition are very effective. 
numerous examples from works practice, some of 
which are of special interest. 
The defects commonly found in tools as the 
result of heat treatment, their cause and preven- 
tion, are discussed in another chapter, and many 
useful and practical hints and suggestions are 
given which form a valuable contribution to the 
literature on heat treatment. 
The author states that the practical details have 
largely been compiled from his works notes, 
made for his own guidance during twenty-eight 
years, and, as is almost inevitable in such cir- 
cumstances, certain portions of the book suffer 
from their being somewhat disconnected; but this 
is a small matter, and in no way detracts from 
its value and usefulness. 
F. W. Harsorp. 
Le Transformisme et l'Expérience. By E. 
Rabaud. Pp. vii+315. (Paris: Félix Alcan, 
1911.) (Nouvelle Collection Scientifique. Direc- 
teur: Emile Borel.) Price 3.50 francs. 
Tus is a book on the same general lines as Prof. 
T. H. Morgan’s “Experimental Zoology.” The 
author points out how very slowly, and almost, as 
it were, reluctantly, evolutionists have become 
definitely experimental—partly because they were 
preoccupied with applying the evolution-formula 
as an interpretation and with following the sug- 
gestions it offered of further morphological or 
physiological research, and partly because bio- 
logical experimentation is really very difficult. 
Nowadays, however, xtiological experiments are 
being conducted in many laboratories, and there 
are several journals specially devoted to their 
publication. What the author has done is to 
supply us with a competent introduction to experi- 
mental transformism. 
The book is particularly strong in its exposition 
of the influence of the environment upon the 
organism, and the chapters dealing with the 
modifying effects of pressures, the chemical 
medium, humidity, heat and light, climate, and 
They bring together 
/in a clear and scholarly way a large number of 
scattered facts bearing on modification. As it 
seems to us, the author has allowed himself to 
become dominated by what is certainly a truth, 
that the environment holds the organism in its 
grip, and is continually provoking it to change. 
Tie has no room for what seems to us an equally 
certain truth: that the organism is itself an 
agent, a creative agent, a self-expressing Proteus. 
But M. Rabaud has no patience with neo-vitalistic 
vagaries of this sort. And yet is it quite certain 
that he has done them justice? His reference to 
“intervention suprasensible,” which neo-vitalists 
are not committed to, does not suggest a com- 
plete understanding. I foals 1s 
Reinforced Concrete Design. By Oscar Faber 
and P. G. Bowie. Pp. xix+332- (London: 
Edward Arnold, 1912.) Price 12s. 6d. net. 
As the authors point out, the art of designing 
reinforced concrete structures cannot be acquired 
solely by studying text-books; practice under 
