Capt. J. Rodgers on Tides at Tahiti. 153 
Taking the mean of all the observations we find 59 minutes 
ast noon, and 58 minutes past midnight, for the average time of 
igh-water, and 45 minutes past six for the average time of low- 
water, both morning and night. 
The smaller diagram shows the variations from that mean, 
arranged according to the moon’s transit. The curve exhibited 
might be called the half-monthly inequality in the soli-tidal in- 
terval, in analogy to the curve of half-monthly inequality of the 
luni-tidal interval of ordinary tides. 
ith regard to the heights, the statements received are not 
quite precise as to the scale used in the self-registering tide-gauge, 
and some uncertainty arises from the zero-point having been re- 
peatedly altered, owing to the necessity of using the same paper 
on the gauge several times. On the best supposition that can 
be made we find the mean rise and fall to be 0°87 ft. The ob- 
servations made at the same port, fora few days, by Capt. Sir 
Edward Belcher, R. N., in 1840 (Phil. Trans., 1843) gave a mean 
rise and fall of only 0°56 ft. The diurnal inequality is well 
marked, and the half-monthly inequality regular and normal. 
we examine the variations of the intervals near the time of 
apply mutatis mutandis to the midnight tides. 
he range of the tides seems to be considerably less near the 
Solstice, than they are near the equinox. : 
here seem to have been some notable changes in the mean 
level of the ocean in the month of July. 
ce but no answer has ever been received. It has been thought 
advisable therefore to publish the results as far as the 
: obtained. ; 
Am. Jour. Scr.—Srcoxp Serres, Vor. XLI, No. 122.—Mancs, 1866. 
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