January 28, 1904] 
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291 
animals of the chase; food-fishes; whales; _pearl- 
mussels. 
Group B.—Animals bred or cultivated by man for 
food or for the use of their products in industry or for 
their services as living things. Examples :—flocks 
and herds; horses; dogs; poultry; gold-fish; bees; 
silkworms and leeches. 
Group C.—Animals which directly promote man’s 
operations as a civilised being without being killed, 
captured or trained by him. Examples :—scavengers 
such as vultures; carrion-feeding insects; earthworms 
and flower-fertilising insects. 
Group D.—Animals which concern man as causing 
bodily injury, sometimes death, to him, and in other 
cases disease, often of a deadly character. 
amples :—lions; wolves; snakes; stinging and para- 
sitic insects; disease-germ carriers, as flies and mos- | 
quitoes; parasitic worms; parasitic Protozoa. 
Group E.—Animals which concern man as causing 
bodily injury or disease (both possibly of a deadly 
character) to (a) his stock of domesticated animals; 
or (b) to his vegetable plantations; or (c) to wild 
animals in the preservation of which he is interested; 
or (d) to wild plants in the preservation of which he is 
interested. Examples :—Similar to those of Group 
D, but also insects and worms which destroy crops, 
fruit and forest trees, and pests such as frugivorous 
birds, rabbits and voles. 
Group F.—Animals which concern man as being 
destructive to his worked up products of art and in- 
dustry, such as (a) his various works, buildings, larger 
constructions and habitations; (b) furniture, books, 
drapery and clothing; (c) his food and his stores. 
Examples :—White ants; wood-eating larve; clothes’ 
moths, weevils, acari and marine borers. 
Group G.—Animals which are known as ‘ bene- 
ficials*’ on account of their being destructive to or 
checking the increase of the injurious animals classed 
under Groups D, E, and F. Examples :—Certain 
carnivorous and insectivorous birds, reptiles and 
Amphibia; parasitic and predaceous insects, acari, 
myriapods, &c. 
We have, then, in this ‘ First Report on Economic 
Zoology ”’ a large number of expert discussions of 
particular points—all of practical importance and some 
of theoretical interest as well; and we have also a 
luminous orientation of the whole subject. No one 
can help being impressed by the fact that zoology 
does not lose either in interest or in thoroughness as 
it becomes more social. NAL TD: 
IRRIGATION WORKS. 
Irrigation Engineering. By Uerbert M. Wilson, 
C.E. Fourth edition. Pp. xxiii+573. (New York : 
John Wiley and Sons; London : Chapman and Hall, 
Ltd., 1903.) Price 17s. net. 
A N annual grant of about 500,000l. having been 
4 recently allotted by the Congress of the United 
States for the construction of irrigation works in arid 
regions, under the supervision of the director of the 
Geological Survey, various projects have been prepared 
NO 1787, VOL. 69] 
Ex- | 
| disposal. 
with a view to their execution in the near future, which 
have already given employment number of 
engineers. This development has enhanced the im- 
portance of a sound knowledge of the principles of 
irrigation engineering, and has, accordingly, led the 
author to revise thoroughly and enlarge his book on 
the subject. 
The area of land irrigated in the United States, 
reaching more than 73 million acres, is second only 
to India with 33 million acres, being larger than the 
irrigated area in Egypt of 6 million acres, in Italy of 
4; million acres, and in Spain of 2% million acres. 
The States in which irrigation has been most resorted 
to are Colorado, California, Montana, Utah, and 
Idaho, with irrigated lands ranging from 14 million 
to half a million acres. After a very short introduc- 
tory chapter on irrigation, the bool is divided into 
three parts, dealing with hydrography, irrigation 
canals and canal works, and storage reservoirs re- 
spectively, in nineteen chapters altogether. 
The subjects treated of in the first and third parts 
are, for the most part, similar to those contained in 
books on water-supply, the chief exceptions being 
chapter iv., on alkali, drainage, and sedimentation ; 
chapter v., on the quantity of water required; and the 
end portion of the last chapter in part i., relating to 
sewage irrigation, which belongs strictly to sewage 
When the drainage of irrigated lands is not 
efficiently provided for, and an excess of water is care- 
lessly distributed, any allxali in solution in the water 
accumulates by the evaporation which occurs as soon 
as the water rises to the surface, sodium carbonate 
being the most injurious to the soil; and the land also 
becomes water-logged and swampy, which, besides 
being bad for agriculture, is liable to occasion malarial 
fevers. Silt, which is brought down in large quanti- 
ties in flood-time by many rivers, the waters of which 
are used for irrigation, is very valuable as a manure 
if it can be spread over the land, but it is very liable 
to deposit in the storage reservoirs and canals provided 
for irrigation, before the water reaches its destination ; 
and the aim of the engineer is to convey the lighter 
and more fertile silt on to the land with the water, and 
to arrest the heavier silt before it reaches the reservoir, 
or to scour it out through sluices in the dam; and in 
the case of a diversion canal from a river, to arrange 
its entrance so as to keep out most of the heavier silt, 
and to male the remainder deposit in a part of the 
canal from whence it can be readily removed. The 
amount of water required to irrigate a given area de- 
pends upon the conditions of the locality and the crops 
raised, and forms the basis of all irrigation schemes. 
The second part deals with works relating ex- 
clusively to irrigation in seven chapters, in which in- 
undation and perennial canals, their alignment, slope, 
and cross section, headworks and diversion weirs, 
scouring sluices, regulators and escapes, falls and 
drainage works, distributaries and the application of 
water and pipe irrigation, are successively considered ; 
and this constitutes the most important part of the 
book as regards irrigation. The book, however, as a 
whole, deals with the principles and practice of irriga- 
tion in a very complete manner, and is profusely illus- 
to a 
