THE LATITUDE-VARIATION TIDE. 
121 
PULPIT HARBOR. 
mm. 
t reckoned in days from February 3, 1879. 
Minimum, 1878, August 22 ± 10. 
Maximum, 1879, March 25 ± 10. 
Comparison with Other Results. 
In the United States Coast and Geodetic Survey Bulletin 
No. 32, page 112, the corresponding term in the latitude- 
variation, as derived from elaborate zenith telescope observa¬ 
tions made at San Francisco for the purpose of determining 
that variation, is 
t reckoned from January 0,1891. Comparing this with the 
result from the tidal observations at San Francisco, we 
obtain a period of 
d. 
427.8. 
The interval between dates is over 18 years; hence this 
value of the period is entitled to great weight. The diver¬ 
gence of the axes is seen to be identical with that derived 
from the tidal observations at the same station. 
In No. 3261 of the Astronomische Nachrichten, Dr. Bak- 
huyzen gives the results of his search for the latitude-varia¬ 
tion tide, using the tidal observations for the 38 years 1855 
to 1892, inclusive, from a mareograph at Helder, about 40 
English miles north-northwest of Amsterdam. The series 
covers practically the same years as that at San Francisco, 
and hence the results should be directly comparable without 
sensible error arising either from variability of the period 
