THE REV. W. WHEWELL’S RESEARCHES ON THE TIDES. 
163 
to establish so curious a rule as this. I think no one looking at the observations 
thrown into the form of curves, will doubt that in them a rule of this kind really pre- 
vails ; but I quite agree with the opinion, that in order to fix the rule with exactness 
a larger series of careful observations is requisite. In order that the reader may judge 
for himself, I annex the figures given by the observations for June 1828. 
Petropaulofsk Heights. 
June, 1828. 
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 
I shall proceed to point out a few additional inferences which offer themselves as 
resulting from the Petropaulofsk tidal phenomena, before I proceed to the observa- 
tions made at other places. 
Single-Day Tides . — The tides of Petropaulofsk show more clearly than any that 
have yet been examined, the manner in which the diurnal inequality may be so large 
as to lead to the appearance of only one tide in the twenty-four (lunar) hours. This 
will be very readily seen, if we follow the motion of the surface of the water for a few 
days, which is done in the accompanying figure. 
June, 1828. 
17 18 19 20 21 22 23 24 25 
The vertical lines in this figure represent the heights of the surface, and the hori- 
zontal space measures the time, each division being a day. It will be seen that there 
are on each day two high waters, excepting the 21st, when the second high water 
passes over to the 22nd, in consequence of the lunar being larger than the solar day. 
The heights of the high waters are alternately greater and less ; as are also, in a still 
y 2 
