The morning call. [volume] (San Francisco [Calif.]) 1878-1895, 1892-07-21
THE DAVIDSON SURVEY.

The report of Professor George Davidson
of his work Of triangulation. while chiefly
intended for SCIENTISTS contains much that
is interesting to the average lay reader.
His object was TO complete the lines of
triangulation along the thirty-ninth paral-
lei from the Atlantic to the Pacific, and the
station he chose Tor bis observations was
the top of Mount Diablo, while his assist
ants occupied the SUBMITS of Mount
CONFESS and Mount Mocho. The measure
mentS were made to Round Top, which the
eastern triangulation strikes. Some notion
of the extreme eXactness of the measure
ments may be formed from the fact that
the limit of error from DabIo to Round
Topic miles-is three feet II projected
to New York, the probable error in the line
would not exceed FIVE feet. 1t is not easy
for a surveyor to measure a large field with
out making larger proporiionate error
han this; so that AS a matter Of fact, we
can measure the continent. with the aid of
instruments, as accurately as we can
measure farm, and more accurately than
surveyors generally measure a county.
From the top Of Mount Diablo Professor
Davidson contemplated panorama which
it has been given by few TO see. It's actual
area was 5000 square miles of land and
tant; ana he could see the electric lights OF
Sacramento, Stockton. Haywards, San
Francisco and its suburbs, besides Benicia
and Vallejo. lying at bis feet. He could
follow the line of the Serras from beyond
Lassen buttes TO Mount Whitney, 222 miles
distant Looking toward Mount Uonness,
just before sunrise. he observed that the
SUMS rays struck the top of that mountain
thirteen or fourteen minutes before they
reached Diabo. The ridge Of the Sierra
was outlined against the flush of sunrise
Ike a blue saw. The distance was 1i3
miles, but it appeared much less.
The heliOtrOpe signals were seen through
the glass at a distance Of 1872 miles, and
with the naked eve at a distance of 100
miles. The professor thinks that By Selling
the moment of greatest infraetion. which is
at sunrise, il might be possible TO see the
top of Mount Shasta from Diablo-the dis
lance being pa miles. Human vision GER
taInly never extended so far before. The
reader will, of course, understand that at
such distances opaque objects are invisible
What is seen is the fash of the suns rays in
a small mirror, ranging from one to eight
inches square. II is with these mirrors that
conversation is carried on over these
enormous spaces
One Of the most beautiful sights seen by
the professor was the fog rolling in from
the ocean. He could see it gather out at
sea and then come swring through the
Golden Gate in mass over half nile thick
Sweeping UP the river it would strike the
Contra Costa hills and sometimes enyelop
them like wave of the sea or a tremendous
snowstorm, sometimes it would rebound
from them and soar into Tie air like the
spray from the waves dashng against a
rock. The fOgs would be so dense that fly
ing scud driven inland above them by the
wind would project its shadow on the sur
face of the fog and present the beautiful
phenomenon known III Europe as the broc-
ken.
Besides establishing his lines of horizontal
distance for the completion of the geudetic
survey, the professor determined accurately
the height of = number Of the peaks In our
mountain system. Mount Whitney over
tops them ali with height of l4,552, Shasta
follows close with IA. 440 then come Dana
and Lyell with 1920 each. CONFESS with
12,5 500, Round Top aud Hoffman each with
something over 10G0), and so on till we
come to Mount Hamilton with 1909. Mount
Dablo with 3S4S, Tamalpais 2640, and so
forth. In mountain heights we must yield
precedence 10 Oregon, Washington and
Alaska, but on the other side Of the Rockies
California need fear no rivals.
1t is a gratifying circumstance that in the
great wOIk Of measuring the globe on which
we live, task in which all civilized nations
are now engaged, the work which has been
done in this State will compare favorably
in point Of minute accuracy with any for
eign work, not excepting the admirable per-
Torrance of the French ngineers In France,
Spain and Africa. We are long way out
OF the beaten track of science, but so long
as We have with US Professor Davidson and
such assistants as young Mr.. EdmuDds We
seem to be doing as much for human knowl-
edge as much older communities.