The San Francisco call., 1910-02-13

forward through the pile. avoiding.
however, the tunnel of any fellow ex-
cavator. and steadily growing in size
until his burrOw is equal IN diameter 70
that of a lead pencil IN from one 70
four years a new pile, exposed to such
an attack. Will he entirely riddled So
that il can be tOppled over by a blow
The limnoria, the aquatic relative OF
the common wood louise or sour bug,
tunnels into woodwork below water I'm
the same manner that his brother on
land burrows into dry timber
As a pile foundation is usually the
only practicable way of supporting a
structure on deep mud or sand several
methods have been devised to circum-
vent these two Industrious workers.
Sometimes when the piles are not too
long, they are made Of cast iron. al
though this is expensive. Sometimes
the pile is steamed in bath OF creO-
sote. a substance distasteful to either
pest: but this process is not only ex-
pensive. but leaves the timber brittle
and still liable TO deterioration from
decay.
The method originated by San
Francisco engineer and largely used In
building docks on the San Francisco
water front offers one OF the best So
1utions of the difficulty. The founda-
tion piles are driven in groups of three;
then jacket. either of wood staves1"
held together barrel fashion. or of steel
plates riveted like a boiler. and long
enough 10 reach from the top Of the
piles we'll down into the mud. Is low
cred over them. and this cylinder
around the piles is filed solid with
concrete
1t is on such foundations that the
light stations at Oakland harbor and at
southampton shoal have been built
The Oakland harbOr light marks the
entrance to San Antonio creek. the es-
tuary along which Oakland's commerce
centers The lighthouse here was de-
signed as an "OffshOre' station. with
complete quarters for two keepers. but
recently the ferry terminal OF the west
ern Pacific railroad was located in the
rear, and the apron OF the ferry slip
now entirely surrounds the light sta
ton. This is one Of the newer stations.
and was built in 1908 TO replace
smaller and inadequate structure.
Southampton shoa1 light station
marks a dangerous shoal In the center
of the northern arm Of San Francisco
bay 1t also contains quarters for
two keepers and in compensation for
the greater isolation these are more
commodious than the quarters at Oak
land harbor. Both stations have small
lights, as they are not intended 20 be
seen at great distances. Oakland har-
Dor has a fixed white light OF the NTH
order and Southampton a lens lantern.
Both sound bells as a warning during
foggy weather.
Above Southampton. where San
Francisco bay grows narrow before 1t
again expands into San Pablo bay. on
the larger of two rocky islets extend
ing crosswise of the channel rise the
tower and piQnacles of East Brother
island light station. a relic OF the East
lake school Of architecture, popular in
the seventies. East Brother has lens
of low power a fourth order fixed white
light being displayed there. but
powerful steam fog signal directs navi
cation up and down the straits during
the fOgs which often hang over them.
The Mare island light station occu-
pies picturesque location at the east
ern end of the island. at the turn OF \
the course leading to the navy yard and
to Vallejo and Napa.
Across from Mare island. at the end
of a wooden jetty which runs out half
a mile from shore and was built for
the purpose of keeping the channels to
the river and TO Vallejo clear of mud.
a new light station is being erected.
Congress in its 1907 session apprOpri-
ated $4,000 for the construction of q
light and fog signal station here at
CarQuinez straits to protect the rapidly
increasing river traffic.
Roe island reef on a reedy island in
Suisun bay, well above Benicta and
Port Costa. is the most inland light sta
tion in the vicinity of San Francisco.
Beyond this point. as well as between
it and the ocean, many beacOns burn
and many buoys and day marks are set
to give warning of submerged rocks
or dangerous shoals.