152 Rev. G. 8. Lyman ox the 
become larger, and not unfrequently boulders are noticed of 
considerable size. The quartz is so uniformly associated with 
the gold, that even the most unscientific explorer would not 
think of looking for the metal where quartz did not abound. 
Passing up the mountains, it is easy to tell when you leave the 
region of gold from the sudden disappearance of the quartz. 
In August of last year, in company with Mr Douglas and 
others, I ascended from the “ dry diggings” near the Rio de 
los Americanos, to within a few miles of the snow, enjoying 
in the highest degree the sublime scenery presented by lofty 
and precipitous mountains, separated from each other by 
dark, deep ravines, and wooded with primeval forests of 
towering firs and pines. The back bone of this mountain range 
is granite, the several varieties of which constituted almost 
the only rock visible in the last few miles of our journey. In 
descending, we passed successively several forms of gneiss 
and other primitive and transition rocks, till we reached the 
slate-formation which prevails in this part of the gold dis- 
trict. We penetrated on this occasion some forty or forty- 
five miles beyond the “ dry diggings ;” and after leaving the 
quartz twelve or fifteen miles up, scarcely a particle of gold 
was discovered. 
As I have mentioned, the prevailing rock of the gold re- 
gion, near the Rio de los Americanos, is slate. There are 
many varieties of it ; some shaly and friable, others hard and 
massive, somewhat resembling greenstone. The laminz of 
the slate-beds are nearly perpendicular, and their direction 
about NNW. and SSE, or nearly the same as the direction 
of the range. These slate-beds often include dykes and beds 
of quartz rock several feet in thickness. At the dry diggings 
above named, I passed at right angles over the upturned 
edge of continuous strata of slate, a distance of four or five 
miles; and in the same direction, slate-beds occur several 
miles farther on, but I had not the means of knowing that 
they were part of the same great deposit. 
In some of the richest explorations yet made, this slate- 
formation immediately underlies the stratum of drift or dilu- 
vium which contains the gold, and much of the gold is found 
in the crevices of the slate, the rough edges of the upturned 
