The republic. [volume] (Washington [D.C.]) 1849-1853, 1853-02-24
oFFtcfAts


COAST Survey OErIcE, February II, 1853.
on: I'm at present ergAge in preparing notes
0n mo tiaes OF the western coast of the United
states and believing that In advance of them q
1etemens OF the general results for San Francisco
4tliiornl9 may be of service to navigators. have
honorto submit it herewith, and to request ar-
thority for it publication. have avoided the use
Of scientific terms, except such as are familiar q
seamen.
NOTES ON THE TIDES Ar SAN FRANCISCO
CALIFORNIA.
Besides the ordinary changes in the time and
height of the tides known to all navigators, it il
important to note the following, generally appli,
cable to the western coast, and particularly to San
Francisco bay. They relate to pecularities In the
tides which occur on the same day. the necessity
for knowing which 10 shown by the fact thst rock
having foe feet and a half of water upon il at lou
tide, may at the succeeding otc tcater on the same
day be awash: ~
l.. The tides at Rncon point. in San Francisco
bay, consist generally Of large and small tide on
the came day; that oftwo successive high waters
in the twenty-four hours, one is much higher than
the other, and of two successive low waters, one
is much lower than the other.
2. The difference in height of two successive
tides (either high or low waters) varies with the
moons decIination. When the declination is
nothing; the difference is nothing, or very small
When the declination is greatest, whether south
or north, the difference is greatest.
When the moon's defamation is nearly,notting,
the intervals between two successive high or two
successive low waters are nearly twelve hours and
differ most from this when the moons dcclination
ia greatest.
8. The inequalities in the heights Of successive
low waters are more considerable than those of
successive high waters; while, on the contrary,
the inequalities in the times of high water are
more marked than those of low
4. The average difference between the heights of
two successive high waters is one foot four and
hal <f
feet and four inches. The average difference of
these same heights, when the moons decEnation
greatest, is for the successive high waters two
feet and for the low waters three feet six inches
The average variation from twelve hours in
the interval between two successive high waters is
three Quarters of an hour. and between two success
sive low waters half an hour The average varia-
tons Of the same intervals when the moon is fur
thest from the equator are respectively one hour
and three quarters of an hour.
g. When the moons sdeciinntion is north, the
higher of the two high tides of the twenty four
hours is the one which occurs about eleven and
half hours after the moon crosses the meridian,
(souths) and when the moon g declination isseuth
the one which occurs about one hour and a half
after the moons meridian passage, (southing)
8 bis. Or the following rule may be used,
which applies when the moon crosses the meridian
between midnight and liz a. m, or between
and ii D. m. +f,st. .a,,ssa
If the moon is south OF the equator, and passes
the meridian (souths) in the morning, the morn
ing nlgh water VIII be higher than the afternoon
high water; if in the af ernoon, the afternoon high
Ter will be the higher.
If the moon is north of the equator and passes,
the meridian (souths) int the morning, the afternoon
high water will be the higher; if in the afternoon,
the morning high water will be the higher.
s I. The lowest of the two successive low waters Of
the twenty four hours occur about seven hours
after the highest of the two high waters.
s. The average difference between the height of
the highesh high water and of the lowest low water,
is five feet eleven and half inches, and the great
est difference is seven feet ten inches. ~
Very respectfully, yours, f
(Signed) A. d. BACHE,
Superintendent.
Hon. THOMAS CoRwIN,
Secretary of the Treasury