The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1898-05-27
PHENOMENA OF Eos.
Sometimes a. Barrier to Sound as Well as
20 Sight.
[oan francisco Chronicle.

Familiarity with the local phenomena
of fog has destroyed interest In them in
the minds of the average San franciscan
He looks on with indifference almost
daily through the summer season on the
marshalling of the fieecy aerial hosts
along the ocean shore line of the city, of
the forcing by them of the Golden Gate,
their assault of the mission heights, their
sweeping charge over the city, their
observation of the Contra Costa range,
and their capture Of the bag. The warn
ng toots of 6ugs and steamers and ferry
boats the ringing of alarm bells at the
various ferry landings, and rhe doleful
cries of the Goat Island and Point Bonita
sirens have to him no special signif-
canoe. And yet these familiar fog phe-
nomena furnished Bret Harte with a
theme for piece Of the finest descript
writing that ever flowed from his pen.
Whence comes the great gray bank of
log that is carried By the strong western
trade winds to the coast line and to the
gates of the city with the setting of the
summer sun, is matter OF as much
winds before which the fog bank is
driven inland. 1t has been inferred that
the trade winds are created by tine heat.
ing of the great interior valley and the
thrush of the colder air of the sea to suI.
ply the vacuum which the heating
process produces. Thus the warm air,
which has been laden with moisture by
solar evaporation far out at sea, is drawn
iushore over the cold northern currents
that sweeps down the coast, condensing
the vapor into dense and chilling fog. :.
While this phenomena is present on the
greater part of the coast line, it is more
conspicuous in the vicinity of San
Francisco than any other part of it.
which gives weight to the foregoing
theory Of its origin, as the Golden Gate
and the low-lying hills of the San Fran
Disco peninsular furnish an unobstruct6
avenue for the aerial currents from the
sea to enter the heated central basin Of
the State, reducing the temperature of
both day and MI ht to that pleasant moan
which makes the California climate
matohless among the climates of the
earth. And the dense redwood forests
which extend along the coast from
Monterey Bay to the Oregon line draw
their sustenance from the summer fog
drift, for as it passes through their tall
tons it is held and condensed in the en-
brace of their branches into drizzle that
drenches the soil in which their roots are
grounded.
In the winter the meteorological
student finds in the fog drift in San
francisco Bay important and almost un-
failing weather signs. Three consecutive
foggy days and nights are almost invari-
ably forerunners of a rainstorm. They
are usually followed by strong south
easter, which drives the fog out of the
bay and brings with it the rain laden
clouds that have been formed in the Gull
Of California to drench the earth owe,
which they pass.
10 the San Francisco fisherman the fog
drift is an open BOOK. He knows through
it's signs the condition of the weather in
the outer roadstead without consulting
either the Weather Bureau or the lookout
at the Point Lobos signal station. If the
bay is full OF fog and a strong breeze il
ruffling its waters, he knows that it is In
nine cases out of ten comparatively calm
outside and probably clear. If the fog
hank extends like q wall from the Colder
Gate to the Berkeley Shore while the
rest OF the bay is clear, he knows that
The outlet roadstead is clear, but banked
with fog, which, later in the day will be
uriven inshore by the trade wind. His
movements and operations are governed
largely by tie fog signs with which he il
SO familiar, and much of his immunity
from disaster is due to this fog craft
When tha fog settles on the bay not
1niy are all the landmarks shut out OF
the ferry masters vision, but the myster
ious influence of fog on the Transmission
of souna IS so deceptive that the location
of tho siren signals and the steam
whistles Of moving craft is uncertain and
often misleading. 1t is actually or
record that the sound of the fog bell al