AUGUST 19, 1915| 
ample, “a falling body hits the ground with pre- 
cisely the same force as is required to lift it to 
the height from which it falls.” He evidently 
means that the work done in lifting the body is 
equal to the energy which it will expend in falling. 
His instructions as to the measurement of water 
by weirs are too inaccurate to please a water 
engineer, but they are really accurate enough for 
the farmer’s purpose. His descriptions of tur- 
bines are too complex for the farmer and they do 
not show great knowledge Of the subject, but the 
farmer does not need to understand them. The 
author is excellent in describing how to make a 
dam. His description of the dynamo is quite good 
and easy to follow, and it will certainly interest 
the farmer in electricity and cause the farmer’s 
son to study the subject more fully, not merely 
through books, but through simple experiments. 
On practical matters—types of lamps, sizes of wire, 
wire joints, Ohm’s law, wiring the house and 
premises, etc.—the author gives good simple in- 
structions. The last quarter of the book is less 
important; it is intended for farmers who have 
no water power. It describes gas-engine plant 
and accumulators. 
The American farmers have a respect for natural 
science and they are glad to cultivate new ideas. 
We think that the publication of this book will 
induce such men and their families to begin a 
fascinating study at small cost, with results in 
comfort and a widening of the mental horizon 
which ought to fill the town dweller with envy. 
PRINCIPLES OF STOCK-BREEDING. 
Breeding of Farm Animals. By Prof. M. W. 
Harper. Pp. xvii+335. (New York: Orange 
Judd Co.; London: Kegan Paul and Co., Ltd., 
1914.) Price 1.50 dollars. 
EW callings have been more prolific in 
theories than stock-breeding. Many have 
been erroneous, while others which have borne a 
strong semblance of soundness have been inappli- 
cable. Most of them have come from stock-breeders 
themselves; but others, which, as a rule, have 
received more attention, have come from outside 
observers. The great stock-breeders, more 
especially the great improvers, have given little 
heed to any other theory than that which has been 
tersely expressed in the words “put the best to the 
best,” but others have been influenced by other 
theories, although their success in the production 
of good stock has usually been parallel with the 
strength of their adherence to the main theory 
whether that adherence was conscious or uncon- 
scious. After the introduction of printed herd and 
stud books, and therefore of “pure” breeding, the 
NO. 2390, VOL. 95 | 

NATURE 

671 

“pedigree” theory was generally taken to be a 
means of breeding good stock as well as ‘‘ pure” 
stock, and only the very greatest stock-breeders 
stood fast by the “best to best ” theory. 
Like many a stock-breeder, Prof. Harper has 
lost sight of the main theory, and has allowed 
others to intervene. With him the Darwinian 
theory has effect as follows: ‘While the influence 
of climate and locality is great, and the factors at 
work are exceedingly complex, yet from a 
practical point of view we may consider the food 
supply and more favourable conditions generally, 
such as sufficient shelter, proper care, including 
training and developing, as the more important 
causes of variation.” A paragraph is headed 
“Mendelism a Cause of Variation.” And, after 
three chapters on Improvement due, 1, to ‘“selec- 
tion based on records of performance,” 2, to “‘se- 
lection the result of prepotency,” and, 3, to 
“accumulative development,” it is stated ‘that 
the degree of development depends on_ the 
environment, including training, management, 
and the like.” Apparently the weight of Bateson’s 
“Materials for the Study of Variation,’ and 
Mendel’s work has not yet been felt. It is no 
argument for the Darwinian view to say that 
“The thoroughbred horse has increased its speed 
by but eight per cent. in one half a century of 
racing. During this same period the standard- 
bred, a comparatively new breed, has reduced its 
trotting record by 27 per cent.” |The words 
in italics indicate some part of the argument to 
the contrary. 
Parts of the work of Galton and Pearson are 
cited, but with no indication how the formule of 
these investigators, even if sound, are to be made 
use of by stock-breeders; and the idea that “the 
new individual inherits all the characters of the 
race to which it belongs,” which is cited frequently 
and appears to be regarded as fundamental, is of 
very doubtful accuracy when applied to domestic 
animals. In the chapter headed “ Mendel’s Law 
of Heredity,” the statements are made that 
“Mendel made a series of studies . . . from 
which he drew some general conclusions, now 
known as Mendel’s law of heredity,” and 
“Mendel’s Law . . . depends on three factors— 
unit characters, dominance, and segregation.” 
Apparently Prof. Harper has become acquainted 
with Mendel’s Law from later writers rather than 
from Mendel himself. 
In his volume, however, a source of information 
of very great importance is indicated. In the 
United States, careful records have been kept of 
the performances of the Holstein-Friesian breed 
of cattle, and these show that, as they had none, 
or one, or two parents in what is called the ad- 
