1854.] WILSON CALIFORNIA GOLD-FIELDS. 313 



between, so as to be penetrated by roots, and are easily separated to 

 a considerable depth ; but where the mass of earth is considerable, 

 or where water remains on the rock, the decomposing slate forms a 

 bluish-white tenacious clay. 



In the middle of the plain one hill rises rather abruptly to a con- 

 siderable elevation, and has a large vein of quartz running through 

 its greatest length, from which it has obtained the name of Quartz 

 Mountain. This quartz vein can be traced both to the north and 

 south of the hill. To the south it rises high in another hill close to 

 Sulivan's Creek. To the northward it mounts like a wall near to 

 Table Mountain, under the porphyritic rocks of which it passes, and 

 again appears with its associated slate at Mormon Camp, running in 

 the direction of Carson's Hill. The quartz-vein was being worked at 

 all the places here named ; but the richest surface-diggings are at 

 points intermediate, on either side of the line, indicating a greater 

 waste at such places. 



Geological characters of district hettveen San Francisco and the 

 Diggings. — Having business that required my presence in San Fran- 

 cisco, I made a detour by the Calaveras in order to include more 

 mineral country in my route. My first day's journey brought me 

 across the above-mentioned Table Mountain. 



Table Mountain. — This mountain is a remarkable feature in the 

 landscape ; not from its elevation, which however is considerable, 

 but from its perpendicular sides, and long, level outline, extending 

 ten or twelve miles from N.E. to S.W. It is formed of a black por- 

 phyritic rock, which contains a large amount of iron. Crystals of 

 felspar of the same colour as the rock are distributed through it, 

 which become white as they decompose, and which leave their print 

 in the rock when they have disappeared. In some places the rock is 

 compact, and at others rises in the form of irregular columns or 

 palisades. The mountain has no great breadth at any point, while 

 at some places it is comparatively a mere wall. I found it overlying 

 the slate-rock, and at some places, where the mountain presented a 

 perpendicular wall, the slates were also perpendicular, and parallel 

 to it. 



It appeared evident to me that the matter of which the hill is 

 composed had, while in a state of fusion, been injected and moulded 

 in the cavities and rents of the rocks which then surrounded it and 

 stood immensely elevated above its present height. These rocks, 

 being of a softer nature than the rock of which Table Mountain is 

 composed, and having their vertical edges exposed, would be more 

 rapidly decomposed than the intruded porphyry, so that the Table 

 Mountain would eventually, as it does, look over the hills in which 

 it once lay embosomed as a liquid mass. The sharp, high crags 

 of ragged rock which then surrounded it are become low, smooth, 

 rounded hills, and flats covered with vegetation, while the waste 

 drifted from them has covered the valley of the San Joaquin with 

 many feet depth of earth and gravel. 



Origin of the Gold Drift, and comparison of drift and quartz- 

 veins as to their auriferousness. — Thus, we can perceive, how nature 



z 2 



