108 8. F. Peckham—The Origin of Bitumens. 
3d. Those bitumens that form asphaltum and contain paraf- 
ne. 
4th. Solid bitumens that were originally solid when cold or 
at ordinary temperatures. 
The first class includes the bitumens of California and Texas. 
They are doubtless indigenous in the shales from which they 
issue. It is also probable that some of the bitumens of Asia 
belong to this class. 
have described the conditions under which bitumens occur 
on the Pacific coast of southern California in great detail in the - 
reports that I have made to the Geological Survey of that 
The forms of bitumen that are found there are almost 
infinite in gradation, from fluid petroleum to solid asphaltum. 
n Ventura county the petroleum is primarily held in strata of 
shale, from which it issues as petroleum or maltha, according 
stage road from San Buena Ventura to Los An eles, between 
Las Posas and Simi, on an eroded plateau surrounded 
mountains, fragments of scoria are scattered over the ground. 
The Coast Ranges here appear to have been produced by par- 
completely removed and the shales cut away until, at the 
Rincon, east of Santa Barbara, the erosion reaches the sea-level, 
and beyond, to the westward, the upturned edges of the shale 
