THEIR DEPOSITS AND DRAINAGE. 643 
that of Mr. Clarence King, have not yet been given to the 
public, but from an examination of some of the materials 
which are to compose the reports of this expedition, I feel 
justified in saying that it will prove to be among the most 
important of all the series of explorations of which it forms 
a part, and that the published results of this expedition will 
be not only an important contribution to science and our 
knowledge of our own country, but a high honor to those 
by whom the work has been performed, and to the Govern- 
ment by which it was organized. 
Without going into details or citing the facts or authori- 
ties on which our conclusions rest, I will, in a few words, give 
the generalities of the geological and topographical structure 
of that portion of our continent which includes the peculiar 
features that are to be more specially the subject of this 
paper. 
It is known to most persons that the general character of 
the topography of the region west of the Mississippi has 
been given by three great lines of elevation which traverse 
our territory from north to south: the Rocky Mountain 
Belt, the Sierra Nevada and the Coast Ranges. Of these, 
the last is the most modern, and is composed, in great 
part, of Miocene Tertiary rocks. It forms a raised margin 
along the western edge of the continent, and has produced . 
that "iron bound coast" described by all those who have 
navigated that portion of the Pacific which washes our shores. 
Parallel with the Coast Mountains lies a narrow trough 
Which, in California, is traversed by the Sacramento and San 
Joachin Rivers, and portions of it have received their names. 
Further north, this trough is partially filled, and for some 
istance, nearly obliterated by the encroachment of the 
neighboring mountain ranges, but in Oregon and Wash- 
ington it reappears essentially the same in structure as 
further south, and is here traversed by the Williamette and 
Cowlitz Rivers. 
These two sections of this great valley have now free 
