THE CANONS OF THE RIVERS. 63 
The great elevation of the important gravel masses, and the deep cations 
into which the whole mining region is cut up, afford, in almost every local- 
ity, the necessary facilities for arranging the sluices and disposing of the 
tailings. 
From the above sketch of the hydraulic method of mining, in regard to 
which various additional details will be given farther on, it will be evident 
that the deposits of gravel which are of sufficient magnitude to make it 
worth while to construct such costly works for making them available must 
be something very different in character and position from the accumula- 
tions in the beds of the present rivers. And, as it is especially the object 
of the present volume to throw all possible light on the mode of occurrence 
of the gravels worked by the hydraulic method, it will be necessary to show 
in what respect these deposits of auriferous material of such great extent 
and at so high an elevation differ from those which are found in the beds of 
the present rivers. 
Before entering on the proposed description of the mode of occurrence of 
the high gravels of the Sierra, it will be necessary to give some additional 
facts in regard to the form and position of the present river cajions, and their 
relations to the general surface of the slope of the Sierra. To one standing 
on some point, not too elevated, but from which a good view of the surface 
of the country along the flanks of the Sierra may be had, its slope will ap- 
pear to be quite uniform and unbroken, to one looking along a line parallel 
with the general trend of the range. It will seem, provided the point of 
view be favorably selected, as if the whole region was a gently descending 
plain, sloping down to the Great Valley at an angle of not more than two or 
three degrees. And the slope of the Sierra is—in the mining region, at 
least — quite moderate, for if we allow a rise of 7,000 feet from the lower 
edge of the foot-hills to the crest of the range, the distance between the two 
points being about seventy miles, the average rise is only 100 feet to the 
mile, which gives an angle of slope of less than two degrees. And if one 
ascends the Sierra, keeping on the divide between any two rivers in the 
mining districts, he will find himself, for most of the time at least, on what 
seems to be a plain with a very gentle rise.* Let the traveller, however, 
turn, and attempt to make his way across the country, in a line parallel with 
the crest of the range, and he will discover that this apparent plain is cut into 
* The heaviest grade of the Central Pacific railroad, on the west slope of the Sierra, is 105 feet to the 
mile. 
