10 On the Tides of the Western Coast of the United States. 
6. When the moon’s declination is north, the higher of the 
two high tides of the twenty-four hours is the one which occurs 
about eleven and a half hours after the moon crosses the meridian, 
(souths) and when the moon’s declination is south, the one which 
occurs about twenty minutes after the moon’s meridian passage, 
(southing). 
6 bis. Or the following rule may be used, which applies when 
the moon crosses the ga ‘between midnight and 113 a.m, 
or between noon and 114 p 
If the moon is south of the ‘equator, and passes the meridian 
Coratheys in the morning, the morning high water will be higher 
n the afternoon high water, if, in the S ccon the afternoon 
high water will be the higher. 
If the moon is north of the equator, and passes the meridian 
(souths) in the morning, the afternoon high water will be the 
higher; if in the afternoon the morning high water will be the 
higher. 
7. The lowest of the two successive low waters of the twenty- 
four hours occurs about seven hours after the highest of the two 
high waters. 
8. The average difference between the height of the highest 
high water and of the lowest low water is five feet eleven, and 
the greatest difference is seven feet seven. 
Arr. II.—Comparison of the diurnal inequality = the tides at 
San Diego, San Francisco, and Astoria, on the Pacific Coast 
of the United States, from observations in connection with the 
Coast Survey ; by A.D. Bacue, Superintendent.* 
(Communicated to the American Association for the Advancement of Science, 
by authority of the Treasury Department.) 
Ar a meeting of the American Association in August, 1853, I 
submitted some remarks on the diurnal inequality of the tides as 
observed at San Francisco. I propose now to compare this im- 
portant ae at the three ports of San Diego in California, 
o in California, and Astoria in Oregon. The results 
are the first £ fruits of the tidal observations under the immediate 
charge of Lieut. Trowbridge, of the Corps of Engineers, _ a 
which I referred at the same meeting, as in progress. The seri 
is intended to develop the tidal phenomena of that coast, and she 
three stations referred to are those for permanent reference, at 
which self-registering tide-gauges have been re- 
sults now communicated are derived from observations at Asto- 
* From Report of the Superintendent of the Coast Survey, ot aie the Progress 
of the Survey during the year 1854, p. 152. Washington: 1 = 
