THE GRAVEL DEPOSITS: BETWEEN THE YUBAS. ~* 199 
With the above rapid sketch of the facilities for procuring water on the 
divide between the Middle and South Yuba rivers, we may proceed to a 
statement of some facts in regard to the gravel deposits. 
A reference to the map will show that there is a continuous capping of 
lava on the ridge from Eureka down as far, nearly, as North Columbia. Be- 
low here is only one isolated patch, at Montezuma, about a mile and a half 
long and pointing directly toward the isolated lava-capped hills mentioned 
as lying near the Key-Stone saw-mill. Of the thickness and character of the 
volcanic capping the writer knows almost nothing. Neither are there any 
details of altitude for this region, the elaborate series of barometrical obser- 
vations of the Geological Survey, of which the tabulated results are given in 
the Appendix, having been discontinued on reaching the South Yuba. In 
general terms, however, it may be stated that the summit of the ridge, at its 
lower extremity near French Corral, is a little over 1,000 feet above the 
surface of the water in the Yuba; also that the height of the flat portion of 
the ridge, above the river valleys north and south, increases gradually as we 
go up the divide; but that the depth of the caiions in this region is not so 
great as it is farther south among the branches of the American River, or 
farther north in Sierra County. Still, there is ample room for tailings in the 
various steep ravines which furrow the sides of the central high divide, whose 
table-like top rises on the whole with rapid and regular grade towards the 
granitic High Sierra region, where lie the various reservoirs which have been 
mentioned, and which appear to be at an elevation of about 6,000 feet. 
There is on this ridge, and especially towards its lower portion, a large 
area of gravel uncovered by any volcanic capping, of very remarkable thick- 
ness, and most of it not so compacted together that it cannot be moved 
by the hydraulic jet. It is also apparently auriferous throughout, so that with 
large supply of water available, as already described, this portion of the State 
offers a most favorable combination of conditions for the development of the 
hydraulic mining industry on a grand scale. <A brief account of the opera- 
tions going on in this region will be given here; but with the expectation 
that a fuller one will follow in a supplementary chapter or appendix to this 
volume. 
The general position of the uncovered gravels in the region between the 
South and Middle Yuba rivers will be seen on the map, as well as the names 
according to the amount utilized. This includes repairs and all expenses, but not interest on the cost of 
the property and improvements. The selling price varies from sixteen to thirty cents per 24-hour inch, 
according to the locality where delivered. 
