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2 On the Tides of the Western Coast of the United States. 
one of great age importance to the navigator; for, in San 
“Francisco bay, a rock which has three and a half (32) feet of 
water upon it at he morning high water, may be awash at high 
water ofthe afternoon; and charts, of which the soundings are 
reduced to.mean low water, will have no accurate significance, 
being liable to an ete ae me of the soundings at either low 
water of the day, of 1-18 
The results which T ee atin and propose to discuss, are of 
two series of tides observed In connexion with the Coast Survey 
at Rincon Point, in the city of San Francisco, California. The 
observations were under the direction of Lieutenant Commanding 
James Alden, U. S. Navy, one of the assistants in the Coast Sur- 
vey. They were made hourly, except about the time of high 
and low water, when the regular intervals were fifteen minutes, 
and the attempt was made to seize the precise time of high and 
low water. 
The first series extended from January 17 to February 15, 
1852, and the second from January 23 to February 17, 1853. 
Another set of similar observations was made at Saucelito, on 
the northern side of the Bay of San Francisco, but not with the 
same care which appears to characterize these. The results are 
in general accordant with those deduced from the Rincon Point 
serie 
The reduction of the work of 1852 was made by Mr. W. W. 
Gordon, and that of 1853 by Messrs. Fairfield, Mitchell, and 
Heaton, of the tidal party of the Coast Survey office 
The results of 1852 are projected in the curves shown in dia-~ 
gram A, where the abcisse represent the times from 0 hours mid- 
night, and the ordinates represent the heights. The scale is such 
that the intervals between the vertical lines correspond to two 
hours, and between the horizontal lines to half a foot. The 
curve begins with midnight of the calendar day, January 16, 17, 
and ends with noon of February 15. e epochs of the moon’s 
phases, and of zero, and of maximum declination of the moon, 
are marked at the head, and the times of transit at the foot of the 
diagram, the curves upon which, for convenience of the page, 
have been divided into two parts, so arranged with respect to each 
other that the days of a al declination fall nearly over 
and under each other. curves of the series of 1853 present 
me same general results, with ‘shone the same extent of irregu- 
arities. 
These tides obviously present a case of large diurnal inequality 
in height ;* the interference of the diurual and semi-diurnal waves 
going to produce one large and one small tide in the twenty-four 
* The quantity given as the diurnal inequality in height, is the whole difference 
the heights of tro masse igh wate ot oy aters and that for the 
interval, the whole difference between the lunitidal interval of two ‘successive high 
waters or low % 
Sa GR Sains ee se ee 
