326 WATER STORAGE AND CANALIZATION. 
water. In the San Joaquin Valley a tract of 1,000 acres of flat 
sandy country, which would in its natural state barely support 
one sheep to the acre, was rendered so fertile with irrigation, 
combined with cultivation, that when sown with alfalfa, a species 
of lucerne, it fed no less than twenty sheep to the acre. In the 
same valley, as noticed above, it was estimated that a large district 
considered previously worthless for tillage would, by means of & 
it. Hydraulic mining has been hardly introduced here, and yet, 
owing to its great economy, it must shortly attain considerable 
importance. According to Professor Silliman’s investigations 12 
California, it took 17,074,758 cubic yards of water to wash 
989,165 cubic yards of gravel by hydraulic sluicing ; at whi 
rate 3,486 gallons would wash 1 cubic yard o gravel, or 3} 
million gallons would wash 1,000 cubic yards, which is about the 
5 eae quantity sluiced away by a first-class hydraulic mine per 
em. i i i i rm 
down the Snowy and Tumut Rivers to the deep gravel drifts 
Kiandra ; for supposing the average depth of these d 
only 90 feet, and the average yield only 3 grains per mar 
yard, then every 10 acres would yield 9,075 ounces of gold, wo 
£44,031 5s. These drifts extend for miles on miles alung the 
