114 
CHRISTIE. 
period of 427 days. After a brief consultation as to the tidal 
observations available, the superintendent directed me, as 
chief of the tidal division, to make a rapid preliminary 
search for the tide, with the understanding that if its exist¬ 
ence were once established a more careful determination 
could be made at our convenience. I made an analysis of 
the subject that evening, the work of reduction of the obser¬ 
vations began next morning, and on February 13, 1892, I 
passed to the superintendent, in writing, the defining ele¬ 
ments of the latitude-variation tide, as derived from the 
observations made at the Coast Survey mareograph stations 
in the immediate vicinity of San Francisco, Cal., namely, 
at Fort Point, latitude 37° 48'.4, longitude 122° 28'.2, from 
February 5, 1856, to February 15, 1870, and at Sausalito 
(formerly Saucelito), latitude 37° 50'.5, longitude 122° 28'.5, 
from February 19, 1877, to March 2, 1891, in the form 
a x cos (i \ 5 — O + a 2 cos (2 i t —■■ e 2 ), 
with 
ft. in. mm. 
a x = 0.066 ■= 0.79 = 20, = 82°, 
ft. in. mm. 
a 2 = 0.038 = 0.46 = 12, e 2 = 16°, 
i — 0°.03428 per mean solar hour, 
d. 
Period = 437.6 days, 
t reckoned from 0 h , February 5, 1856, San Francisco mean 
local civil time. 
I then proceeded to bring into the reduction seven more 
years at Fort Point, thus completing at the two stations, 
which are connected by a line of spirit-levels and may be 
regarded as a single station, a 35-year series extending from 
February 5, 1856, to March 2,1891, constituting 30 consecu¬ 
tive periods of 427 days each; and I revised those portions 
of the whole work where the condition of the observations 
and the inferior character of the tabulations and daily sum¬ 
mations, made many years before, were most favorable to 
the occurrence of error. The result was a modification to 
