350 Prof. A. D. Bache on Tidal Observations. 
researches, I did not suppose that small differences would come 
out of them such as have been deduced. The reference to the 
level of each day compensated in a degree for the effect of an 
entire raising or depressing of the water by the wind’s action. 
The results promising success, the coefficients were deduced 
by the method of least squares for the first, and then for the sec- 
ond six months, and finally for the whole year. These laborious 
computations were made with much skill by Mr. W. W. Gordon, 
of the Coast Survey. The result for the second six months, in 
reference to the coefficient of the term of the sun’s declination, 
is discrepant from the final result ; but as the coefficients for the 
whole year were used, after endeavoring to trace the errors, if 
any, without immediate results, it was not pursued further. 
TABLE No. VL 
Coefficients of cos(p-), deduced from the method of least squares. 
| | B. cos. | B.A. cos ()-9). 
‘| First six months, ........ 1°00 02 
Second six months, ...... 0-90 060 
WO YORE, ois ico ci os 0:96 0-24 
The sum of the positive and negative quantities balance, and 
rather better by the use of the coefficients from the first method, 
which differs chiefly in the coefficient of the sun’s action. 
The coefficient of the first term of dh is Bx(A), and of the 
second term B; and it will be seen hereafter in discussing the 
semidiurnal tide, that (A) is 0:36, which, with B=0-96, gives 
x(A)=0°34. 
A set of tables was next made, containing the values of the two 
terms of the formula for each day. To these was subsequently 
applied the small correction for the parallax from the term pr? 
and the terms, being summed, were compared with the observed 
maximum ordinate, and the difference in the final column of the 
the theory may be followed much more closely by the 
than I had at first supposed. 
