204 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
Humbug Creek, a short distance from the South Yuba River, and follows 
nearly the course of the cation, some 200 feet below its bed. This tunnel, 
which is 7,874 feet in length, hasa grade of four and a half feet in a hundred, 
and is eight feet by eight in dimensions above shaft No. 6. Its total cost is 
stated at half a million of dollars. Other tunnels in this region are: the 
Boston, leading to Woolsey’s Flat, length 1,600 feet, and cost $ 40,000; Far- 
rell, to Columbia Hill, length 2,200 feet; English to Badger Hill, length 1,400 
feet; American, below San Juan, 3,900 feet long, cost about $ 140,000 ; 
Manzanita to Sweetland, length 1,740, cost $62,000; Sweetland Creek, 
also to Sweetland gravel, length 2,200 feet, cost $90,000; Bed-Rock, 
below Sweetland, length 2,600 feet; French Corral, length 3,500 feet, cost 
$ 165,000.* 
The fact that most of the gravel between the Middle and South Yuba riv- 
ers belongs to large companies renders it probable that we shall eventually 
obtain from this region much fuller and more accurate statistics than it has 
been possible to procure from other parts of the hydraulic mining region ; 
where, usually, as will have been recognized from an examination of the 
preceding pages, trustworthy information on most of the important points 
can hardly ever be obtained. Some data of this kind are already — 
at hand, and have been published in the papers of Messrs. Hague 
and Bowie, which have already been cited several times. The investi- 
gations made at the North Bloomfield Company’s works quite harmonize 
with the general result already made evident in the preceding pages of this 
volume, that the particles of gold are in most cases scattered through the 
whole body of the gravel; but that they are more numerous and of larger 
size in the lower portions of the channel, and especially immediately over and 
on the bed-rock surface. The results obtained by Professor Pettee,t in re- 
gard to the small yield of the top-gravel near Gold Run, are quite similar to 
those published by Mr. H. Smith, Jr., the able Engineer of the North Bloom- 
field Gravel Mining Company, of the amount obtained from the upper por- 
tions of their deposit. It appears from his statement, { that this company in 
* Mr. Skidmore, in the Sixth Report of the Commissioner of Mining Statistics, states that the cost of the 
improvements made by three of the principal mining companies in this district, the “ North Bloomfield 
Gravel Mining Company,” the “Union Gravel Mining Company” and the “ Milton Mining and Water 
Company,” had up to 1874 amounted to $3,500,000 ; and that nearly $ 1,000,000 more would be required 
to complete the works then in progress, so as to fully open up the gravel deposits belonging to these 
various companies. 
t See ante, p. 152. 
t Quoted by Mr. Bowie in his paper previously referred to. 
