44 6 A Description of the Process of [August, 
from io to 40 feet per mile as of an ordinary river, and the 
calculated thickness of the alluvial conglomerate is abo 
600 feet in many places across the ridge between the bou 
and Middle Yuba River across the Columbia. The powe 
of the water for the operation is dependent on a give 
volume deposited in a reservoir, and at sufficie , n ^^ e ^ 1 ? t n 
above the points of discharge, as on this depends its e 
ivity to tear down the gravel. It is delivered to the ™ 
by huge pipes made of wrought iron, and laid down to 
follow the curvatures of the surface of the ground ; and the 
pipe I now treat of, belonging to the Excelsior Water Com 
pany, has a diameter of 40 inches on a length of 6000 teet 
and 20 inches on the rest of its length of 3000 feet, beg 
9000 feet in all ; and this large pipe forms an inverted 
syphon across a valley, following on the gravel, to the top 
of the hill into the reservoir. 
These pipes offer advantages over wooden aqueducts to 
spanning chasms, and also to avoid coursing the sides ; 0 1 
valleys ; being also cheaper to construft in general, and less 
liable to accidents from fire and storms, and have the co - 
venience for conveying the water from pomt to point, as the 
work of excavation advances, necessitating the removal ot 
portions of the aqueduCt forward. The watershed, or iesei- 
voir, of the Excelsior Company emoraces the valley of the 
South Yuba and its affluences, and the entire cost ot its 
eight amalgamated canals was 750,000 dollars. < 
The rainfall during three years in the mountains aveiaged 
49 inches annually, whilst the medium in the same period 
did not exceed 20 inches in the plains beneath. The heigh 
of the reservoir above the tailing, or Yuba River, is 393 teet , 
and the height of the head above the floor, or outlet sluice- 
tunnel, of the Blue Gravel Mining Company was 197 feet. 
The exadt quantity of water required to wash every class 
of gravel is difficult to estimate, but no quantity or pressure 
would be excessive if properly arranged. The measurement 
of water is effected by miners’ inches, by allowing it to flow 
from the reservoir of the seller to the purchaser through a 
box 10 or 12 feet square, with divisions to obtain a quiet 
head, with a slide or opening capable of adjustment to any 
required measure : thus an opening of 25 inches by 2 inches, 
with a quiet head of 6 inches above the middle of the orifice, 
would give 50 inches, or about 89,259 cubic feet of water, 
flowing during ten hours per day, being an amount necessaiy 
for a first-class operation. The capability of the Excelsioi 
Canal, in rainy seasons, reached to a delivery in twenty-tour 
hours, to the various mining companies, of 21,120,000 cubic 
