356 | Prof. A. D. Bache on Tidal Observations. 
Another question was, whether the residuals, of which Table 
No. 7 shows a part, contained any portion which varied with the 
moon’s declination. 'T’o test this, the residuals for six months were 
grouped according to the declinations, with the following result. 
TABLE No. XIV. 
Containing the residuals after subtracting the terms containing the sine of twice the 
n’s declination, and the sine of twice sun’s declination, from the macimum 
ine of twice the 
ordinates, grouped according to the values of the sine of twice the moon’s declination. 
| Average value of twice sine ’s declination 
er ee 0 to 20 | 20 to 35 | 35 to 45 | 45 to 55 | 55 to 70 
Average value, ...... “151 "147 | -169 | a a 
No. of observation, ..} (33) (27) (26) (44) (37) 
The result indicates that there is no such term remaining in the 
residual. 
Another question was, as to whether changing the epoch would 
improve the results. Several attempts of this kind were made at 
different stages of the work, but without any marked advantage. 
The average result for the year, as shown by comparing the dates 
of occurrence of the greatest and least maximum ordinate of the 
diurnal curve, and the greatest and least values of the term con- 
taining the moon’s declination, is shown in the next table. The 
comparison is made in two different ways: first, by the date of 
the greatest value of the ordinate shown in the table of maximum 
ordinates; and secondly, by the date shown by the highest pomt 
of the curve, which was traced to represent the observations. 
TABLE No, XV. 
Showing results of comparison of dates of occurrence of the greatest and least mazi- 
mum ordinate of the diurnal curve, and the greatest and least value Te PO 
i ination. 
taining the moon’s declina 
| DATE OF OCCURRENCE—AVERAGE IN DAYS. 
Maximum Maximum | Term embracing | Minimum | Minimum Term ribo 
ordinate ordinate sun and moon’s ordinate ordinate sun and 4 
from table. | from curve. declination. rom table. | from curve,  dectinatos 3 
15-4 16-1 16-0 16°5 Be ie are 
The times of occurrence of the maximum of the diurnal curve 
are, as I have already stated, connected by the hypothesis wit 
those of the semidiurnal curve. The times deducible from ie 
o more than this. Notwithstanding all these irregularities, it 
ble from the results. The average values follow those for the 
semidiurnal curve at the proper intervals. It will be practicable, 
therefore, to resume the examination of this part of the subject, 
which I accordingly purpose to do. 
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