18 
THE REV. W. WHEWELL ON THE TIDES OF THE PACIFIC, 
These observations, especially those south of the equator, appear to imply a general 
motion westward of the tide-wave ; but I conceive that they are much too few and 
too unconnected to justify me in drawing cotidal lines ; besides which, the smallness 
of the tides in the central parts of the ocean makes the observations more than 
usually doubtful, and is accompanied by some circumstances inconsistent with the 
notion of a simple progressive wave as the representation of the tidal phenomena of 
those seas. I will consider those circumstances for a moment. 
Tides of the Central Pacific. 
34. The tides over a great portion of the central part of the Pacific are so small, 
that we may consider the lunar tide as almost vanishing. Thus at Bow Island it is 
stated as only one foot ; at Tahiti it is hardly more ; at the Sandwich Islands it is 
two feet ; and even at New Ireland, where we are no longer in the central space, but 
among the larger islands to the west of it, the tide is only about two feet. But 
moreover at some at least of these places the tide, small as it is, is not the lunar tide 
following its ordinary laws. At Tahiti, for instance, the time of high water appears 
never to deviate from noon by more than a certain difference, although Sir E. Bel- 
cher has shown that it varies from about nine o’clock in the forenoon to three in the 
afternoon*. At Bow Island there appears reason to believe that the limits are much 
the same, and perhaps at Carteret’s harbour in New Ireland. Now it will easily be 
seen that such a result as this would follow, if we were to suppose the tidal influence 
of the sun and of the moon to be equal. On this supposition, it is plain that the 
high water would always occur half-way between the sun’s transit and the moon’s 
transit. Hence at new moon the high water would be at noon ; as the moon went 
away to the eastward of the sun, the tide would be later and smaller ; till, when the 
moon was at 6*^* distance from the sun, the tide would be at 3^ ; but would in fact 
vanish. After this point, the tide would reappear at 9^^ a.m., or a little later, the 
inferior transit of the moon now taking the place of the superior one, in determining 
the tide ; and from this time the tide would be gradually later and larger, till, at full 
moon, it would again be at noon ; and so on. This appears to agree pretty well with 
the phenomena of the tides at Tahiti, as determined by Sir E. Belcher. 
35. A more minute examination of the tides in these regions will enable us to 
pronounce more decidedly whether the law of the phenomena is that which has been 
just stated. And if it appear that the phenomena do follow this law, we shall have 
further to consider how such a motion of the sea in those parts is to be combined 
with the very different movements which occur in other places, and what is the 
general movement of the ocean which they indicate ; whether, for instance, they are 
best explained by looking upon the solar and lunar parts of the tide as produced by 
two separate waves, which may increase and diminish separately, and may start from 
different epochs in their motions. I shall not now pursue this point further ; nor 
* Philosophical Transactions, 1843, Part I. 
