GRAVEL AND VOLCANIC FORMATIONS: CALAVERAS COUNTY. 131 
cially on account of its great depression below the adjacent channel in Table 
Mountain. Until it has been more extensively worked, but little can be 
made out in regard to the connection of this deposit of gravel with any other 
in the vicinity. 
The volcanic formations described as occurring to the west of Vallecito 
Flat extend down nearly to Angel’s Camp, and may be observed in low flat- 
topped elevations on the north of that place and northeast of Altaville. 
There are several alternations of lava and gravel; but the hills are too deeply 
covered with soil to allow the geology to be well made out from an inspec- 
tion of the surface. There have been several shafts sunk and drifts run to 
strike the gravel in this vicinity; but they have not been accessible when 
visited by the writer. What has been ascertained in regard to the details of 
the occurrence of the gravel and lava near Altaville will be noticed in the 
section devoted to the occurrence of human remains at Bald Mountain, the 
famous locality of the so-called “ Calaveras skull.” 
The Sonora, or Tuolumne County, Table Mountain, already several times 
alluded to in the preceding pages, is a lava flow of so much interest, from a 
variety of aspects, that it demands a somewhat detailed description. It is 
perhaps the best marked of all the flows of volcanic materials down the slope 
of the Sierra, not so much on account of its great length, but because it is 
more continuous and more isolated than such flows usually are, as will be 
apparent from the description. It also has a special interest, due to the fact 
that the stratified materials underlying it have been found to contain a con- 
siderable variety of plants and of animal remains, including the bones as well 
as the works of man. The Tuolumne Table Mountain begins in Calaveras 
County at some point high up in the Sierra, which has not yet been posi- 
tively identified. It seems, however, the same flow which is crossed on the 
way from the Calaveras Big Tree Grove to the South Grove, so called, and 
this appears to connect with the lava ridge which is so prominent south of 
Hermit Valley, on the Big Tree and Carson road. At all events, this flow is 
well ascertained to be continuous on the west side of the Stanislaus for at 
least ten or twelve miles above the point where it crosses that river between 
Abby’s and Pendola ferries. On that side of the river, however, there has 
been but little mining done, although the channel seems to have been pros. 
pected, without success, at various points near the river. From that cross- 
ing, which is about on the line connecting Sonora with Angel's Camp, the 
Table Mountain has been cut into by tunnels at quite a number of points 
