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and extending to the 1oo-fathom curve. Beyond this platform the 
descent is usually rapid, 2000 fathoms being reached in from 35 to 100 
miles from the shore. 
In this 100-fathom platform the submarine valleys are found, head- 
ing either close to the shore or only a short distance out, and extend- 
ing to a depth of from about 100 to at least 600 fathoms. These 
valleys vary largely in direction, form, and character of the bottom. 
Four valleys are found off the coast of Lower California and seventeen 
are described from the California coast. They are most numerous 
near the southern end of the state, and near Cape Mendocino, where 
four of considerable size are found within a stretch of twenty miles. 
These four are peculiar in heading under the highest parts of this strip 
of coast, while the majority of the channels are opposite valleys or 
openings in the coast ranges. All of the valleys are described in some 
detail and are well shown by submarine contours on the accompany- 
ing maps. North of Cape Mendocino no submarine valleys have been 
noted with the exception of one indicated near the mouth of the 
Columbia River. 
Although this paper is of importance to geologists, no direct attempt 
is made in it to give the geological bearing of the facts stated. One 
assumption, which is open to criticism, is made by the author in using 
the term ‘‘submerged” where he formerly used “submarine,” to 
describe these valleys, since it is doubtful whether all of them can be 
considered as submerged channels. ‘The studies of the present writer 
on the submarine topography of a part of the California coast have led 
him to the conclusion that no general statement can be made as to the 
origin of these valleys. They may be due to one or more of three 
causes — either (1) they are structural, due to faulting or folding; or 
(2) they are due to the forces of subaérial erosion, and therefore are 
strictly ‘‘submerged valleys ;’’ or (3) they may possibly be due to sub- 
aqueous erosion in delta deposits. Under which of these heads a 
given valley should be placed must be determined by a special study 
not only of the submarine features but of the topography, stratigraphy 
? 
and structure of the neighboring land area, and possibly also of the 
characters of the shore-currents at that point. 
W.S. TANGIER SMITH. 
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