May 10, 1901.] 
provide reservoirs and irrigation works and has 
already done so to some extent, and the ques- 
tion of aid from the national government in 
extending the work is under debate. Much 
light is shed upon what has already been done 
in this direction, as well as upon what is pro- 
posed and is under way, by Mr. Schuyler’s in- 
teresting book, which embodies the material 
used in his reports to the U. S. Geological Sur- 
vey in 1896 and much additional matter of more 
recent date. 
The book is unquestionably a valuable one 
for civil engineers, giving, as it does, a descrip- 
tion of the principal dams built, and now pro- 
jected, in the western portion of the United 
States; and also some account of large dams 
in foreign countries, already completed or in 
progress, such as those at Assuan and Assiout 
in Egypt; giving also (to quote from the title 
page), ‘‘ A discussion of the available water 
supply for irrigation in various sections in arid 
America; the distribution, application, and use 
of water ; the rain-fall and run-off; the evap- 
oration from reservoirs; the effect of silt upon 
reservoirs,’’ etc. In some cases details are 
presented in great fullness; and illustrations, 
views, profiles, maps and plans occur in profu- 
sion throughout the work, thus greatly en- 
hancing its value. As an instance in point, it 
may be noted that in the description of the 
Sweetwater dam, in southern California, built 
after the design, and under the superintendence, 
of Mr. Schuyler himself, there are fourteen 
distinct illustrations (views at different stages 
of construction, sections, maps, etc.), the de- 
scription itself occupying seventeen pages. 
This same dam offers a striking instance of 
the benefits obtained by the erection of such a 
structure. During the thirteen irrigation sea- 
sons up to 1900 ‘the impounded water has 
created values aggregating several millions of 
dollars, reckoning all improvements made in 
the district directly dependent on it for water 
supply.’ Domestic water supply is also fur- 
nished to a population of from 2,500 to 3,000 
people. The cost of the dam was $234,000 and 
thearea at present irrigated from it is4, 580 acres. 
The dams described are classified according 
to their mode of construction and may be 
briefly referred to as follows: 
SCIENCE. 
739. 
‘ Rock-fill’ dams are composed of stones de- 
posited loosely together in a trapezoidal form, 
water-tightness being provided by a sheathing 
of plank on the upper side, or by an earth 
facing. This plan originated some fifty years 
ago in the mining regions of California, when 
the transportation of cement into remote dis- 
tricts was very expensive, or impracticable. 
Later construction employed a concrete ‘skin’ 
on the upper side; or a central and vertical 
steel plate, covered on both sides with hot 
asphalt and burlap, and then imbedded in a 
wall of concrete. Sometimes the steel plates 
formed a facing on the upper side. 
The ‘hydraulic-fill’ dams were composed of 
earth and gravel deposited by ‘sluicing’ the 
material into position; that is, by washing 
down the soil by jets of water from higher ele- 
vations in sluices or pipes into the desired posi- 
tion. In this way, by proper management, the 
finer soil could be made to occupy the center of 
the dam or embankment, while the coarser 
gravel and stones formed the outer portions ; 
and extreme cheapness of construction was 
often attained. Thus, the Tyler dam, in 
Texas, 575 ft. long and 32 ft. high, cost only: 
$1,140 ; including the expense of pumping water 
to form jets for loosening and sluicing the soil. 
As the water drains off gradually the gravel, 
sand and clay are more compacted, it is 
claimed, and hence a more water-tight dam 
obtained, than if the material had been laid dry 
and then tamped. 
Naturally, the chapter on the masonry dam, 
as being the most durable and stable construc- 
tion, occupies a greater space in the book than 
any other. Here the usual arguments are pre-. 
sented in favor of the gravity dam, as against 
the horizontal arch ; though the curved form is: 
advocated in certain cases for esthetic reasons, 
and as providing for remote contingencies. A 
full description is given of that ‘eighth won- 
der of the world,’ the noted Bear Valley dam, 
in California, which with its very slender 
dimensions depends. for stability solely on its. 
arched form ; this form having been given toit 
to effect a saving in the cost of masonry, since 
the cost of hauling cement to the locality was at 
that time (1884) $10 per barrel. The Sweet- 
water dam, already mentioned, belongs to this 
