12 
THE REV. W. WHEWELL ON THE TIDES OF THE PACIFIC, 
vations (Loo Choo, Bonine, Rawak, Giiahan) which show well enough the position 
of the cotidal lines of IX'*., and XR. And continuing these lines with those 
more to the north, we recognise here, with sufficient probability, the same un- 
dulation which, stopped by the coast of Kamtschatka, takes a southerly direction and 
reaches those shores. The difference noticed above between the age of the tide at 
Rawak and at the stations more to the north, agrees very well with this supposition, 
according to which the tide would make three-fourths of the circuit of this sea in 
eighteen hours. 
“ But here we are stopped by a dilemma very difficult to resolve, at least without 
the help of new observations. About 200 leagues to the south-east of the line of 
XL., we should, according to what we have hitherto seen, expect to find the 
line of XIR., or thereabouts. But we find here at two or three places (Ualan, 
Radak, &c.), the tide-hour four hours or five hours, and we ask ourselves what can 
it be which retards the propagation of the tide-wave, so as to make it employ six 
hours in traversing a space which under ordinary circumstances it would pass over 
in one hour.” 
It will appear, I think, from the whole of what has preceded, that this diflSculty is 
one which occurs in every part of the ocean, and can only be explained, or indeed its 
nature ascertained, by drawing the cotidal lines on a larger mass of observations. 
29. Capt. Sir E. Belcher’s voyage has also supplied numerous observations of the 
tides in various parts of the Pacific, which he has kindly placed at my disposal, and 
which have been discussed by Mr. D. Ross of the Admiralty. In like manner Mr. 
Ross has discussed tide observations supplied to me by Capt. Sir James Clarke Ross 
during his last voyage ; also some tide observations by Capt. Stokes, Capt. Kellet, 
and some others which may be noticed hereafter. 
30. I may take the liberty of remarking that many of these observations, being 
given as they were originally recorded, show how very imperfect is the accuracy 
which can be obtained on such occasions, when the series of observations is short 
and the apparatus necessarily rude. They thus show that the “ establishment” de- 
duced from such observations cannot be considered as entitled to much confidence. 
I will, for the sake of example, explain further what I mean. The “establishment” 
is the interval of time by which the tide follows the moon, either at new and full 
moon, which is the vulgar establishment, or its mean value, which is my corrected 
establishment ; and whichever be taken, the term has no meaning, and observations 
made to determine the establishment have no value, except so far as this interval is 
definite in itself, and is determined by the observations. If the tides be regular and 
the observations good, this interval differs from day to day, sometimes as much as 
ten or twelve minutes on successive days, (in virtue of the semimensual inequality,) 
but on the whole fortnight, little more than an hour (its most usual value is P‘ 20”"). 
If therefore this interval, as observed in successive tides, differ by two or three hours, 
there must be some cause of irregularity either in the tides or in the mode of obser- 
