The San Francisco call., 1896-11-04
VALLEYS UNDER
THE PACIFIC
Interesting Lecture by Prof.
Davidson Monday
Night.
The Submarine Elevations and
Depressions Lucidly
Explained.
AN INTERESTED AUDIENCE.
The Subject Has an Important Bear.
ing en- Navigation Not Before
Recognized.

In the hall of the Academy of Sciences
Monday night Professor George Davidson,
at one time chief of the Government Pacific
Coast Survey, delivered lecture entitled,
THE Submerged Valleys of Che Pacific
Coast" This is the third of a series
recently inaugurated by the society for
the purposes of popularizing science. The
large and attentive gathering which
listened to Professor Davidson last night
served to show that the society's laudable
effort is appreciated.
The lecture was illustrated by stereopti-
con views of charts specially prepared by
the professor, whose treatment of his sub
lect proved both instructive and enter
tanning. although many details were
necessarily technical After having re-
viewed at some length the geographical
character of the coast of California he
proceeded to describe still more minuteIy
the submarine depressions and elevations,
which have been referred to, not inaptly,
as valleys and mountains. The Pacific
Coast differs considerably from the At
lantic seaboard in this particular.
Off the coast of New Jersey, far out at
sea, the soundings are invariably shallow,
whereas the "plateaus" of the Pacific are
comparatively few and OF small extent.
Generally speaking, the whole plateau OF
the Pacific. from California to Japan.
averages depth OF 24O0 fathoms, or a
little over 215 miles. The character of the
seaboard, he was careful to point out, is
no indication of the presence of these
submerged valleys. For example, where
we might expect to find one at the open
ing of the Golden Gate, we have instead a
broad plateau. So tar something like
twenty-five submerged valleys have been
Iiccayarad xrst b, IN Gal, ~
in extent they vary greatly. The question
OF their formation he preferred to leave to
the geologist. He merely threw out the
suggestion that it, no doubt, correspondent
with the form alton of American rivers !;
what were formerly mountains became de-
pressed and subsidized below the level of
the sea, the valleys remaining. The dis
great depth of water near the
shore or, at least, where under
ordinary conditions the depth would be
inconsiderabe. The slopes, which rise
on either side of these depressions, are
often very steep indeed, as in the case OF
submerged valley 315 fathoms deep off
the coast OF Southern California, whose
slopes have q grade equal to that of Jones
street between California and Pine. The
bottom usually consists of green and blue
mud, which gives place to sand and shells
as the twenty y-hve-fathom mark is reached.
Oll WellS are sometimes IOunQ at q depth
of seventy five fathoms. One of the most
important of the Pacific Coast submerged
valleys is that which enters Monterey
Bay. This has been chosen as the site on
which to land the projected Pacific cable,
because the latter can be carried into the
beach without exposing it to the risk OF
being fouled by anchors. There are four
notable valleys between Point Arena and
Cape Mendocino, the most southerly run
ming so near the coast that the twenty
five-fathom line is only few yards away
from the shore.
The subject of submerged valleys has
an important bearing upon navigation
not hitherto properly recognized. More
than once, the speaker reminded his hear
ers, vessels have run aground, though
their captains protested that Immediately
before that happened the lead had ind
Gated an ample depth of water. The pro-
fessor expressed his conviction that i'll a
case of this kind, the ship must have
been heading up a submarine valley, in a
dense fog, the shore being thereby rem
dered invisible. Twenty-eight miles from
the mouth of the Columbia River, at
which distance 100 fathoms would ordi-
narily be found, there are 430 fathoms OF
water.
At the end OF his lecture Professor
Davidson showed a chart, prepared last
May, in defense of Nansen's theory of
polar currents. He added few words of
lucid explanation, which were well re-
hvy hiS .r1di