230 
rocks or shales making up the great mass of the mountains 
of the Coast Range which extend down ‘the Pacific shore, 
from Washington Territory to the borders of Lower Califor- 
nia and even perhaps down as far as the southermost extremity 
of that peninsular. These shales are usually of a light 
cream color and mainly consist of the siliceous skeletons of 
Diatomacee and Polycystina; the former being commonly 
considered as plants, the latter as animals. These are of 
extremely minute size and often require for their study the 
use of the highest magnifying powers. Many of them prove 
to be indistinguishable from forms living at the present day 
on the Californian coast. Exuding through and often appearing 
at the upper portion of these rocks, to which situation it has 
_ evidently been driven by heat, is found the Petroleum, 
Bitumen, and Asphalt of California. Hence the Survey has 
conferred upon these strata the name of Bituminous Shales. 
Along the Pacific coast and lying generally parallel to it are 
islands often bearing upon their summits deposits of Guano 
of more or less commercial vaiue. In many cases the quan- 
tity has been small and soon removed, but I am informed 
that there are deposits of this material in that quarter of the 
globe still unworked. At the same time it must be remem- 
bered that the whole Pacific Coast of both North and South 
America is in an almost continual state of motion and grad- 
ual but constant upheaval, caused, doubtless by the action 
of internal chemical changes which make themselves marked- 
ly evident in the volcanic vents found all along the 
mountains constituting the Cascades and Sierra Nevadas of 
North, and the Andes of South America. The Survey 
has been able to identify at least three former lines of rise 
or coast and still another is seen presenting its peaks in the 
islands which will at some future day be united in such a 
manner as to constitute another Coast Range of mountains. 
If now we consider the bearing of these facts on the origin 
of the substance known as Guano we find the following points 
worthy of note. Guano may be divided into two great 
groups, the Ammoniacal and the Phosphatic, but it is of 
the first mentioned only that I desire to treat at the present 
o 
