24 
THE REV. W. WHEWELL ON THE TIDES OF THE PACIFIC, 
to its law, and in a very great degree as to its amount. The sun also will of course 
produce a diurnal inequality, which will depend upon his motions by laws similar to 
those which have been mentioned, and which will combine with and modify the lunar 
diurnal inequality. The determination of the solar, as well as of the lunar effect, is 
requisite, both for the construction of accurate Tide Tables for each place, and for the 
comparison of the tides with their theory. But this regard to the solar effect is not 
needed, either to make up such a general view of the progress of the tides as that at 
which I here aim, or to predict the general course of the tides so as to know whether 
the morning or afternoon tide will be the greater. 
44. In stating that the lunar diurnal inequality alone appears in a conspicuous 
form in the facts, I do not rest merely upon theoretical views or upon a few cases ; 
but am able to show it to be so, by numerous, distant, and extensive series of obser- 
vations. These observations also enable me to trace the course and modifications of 
the diurnal inequality along the greater part of the shores of the Pacific ; and 1 shall 
state their general results for that purpose. 
I shall make this statement in words and figures, without offering to the reader 
any of the diagrams by which the results have been obtained. I am still of opinion 
that by far the best method of discussing tide observations is to lay down the original 
observations (both the heights and the lunitidal intervals) as the ordinates of curves. 
When this is done, the eye perceives at once several of the leading features of the 
case; the diurnal inequality and the semimensual inequality, especially. It per- 
ceives also where the glaring anomalies are ; and we can often thus discern what 
amount of correction of the observations, on the ground of their general tendency, is 
allowable ; and whether, as sometimes happens, the anomalies are so great that the 
observations are worthless. 
45. The mode in which the diurnal inequality shows itself when tide observations 
are thus laid down in curves, has already been presented repeatedly in the Transac- 
tions ; especially in the Sixth and Seventh Series of these Researches*. The inequa- 
lity of heights appears in the zigzag form of the line drawn through the summits of 
the ordinates which represent the heights of successive tides. This zigzag structure 
is sometimes of a moderate degree of abruptness, as in the tides of the coast of 
North America, and of Portugal -f- and those of Plymouth and sometimes extremely 
abrupt, as the heights of low water at lSincapore§. In this latter case, the diurnal 
inequality sometimes makes a difference of no less than six feet between the height 
of the morning and afternoon tide ; the whole rise of the mean tide being only seven 
feet at springs, and the difference of mean spring and neap tides not more than two 
feet. 
In the new observations which I have before me, there are other cases, quite as 
extraordinary as that of Sincapore. I shall now begin to state the general aspect 
of the diurnal inequality, as given by my new materials. 
* Philosophical Transactions, 183G, Part II, ; 1837, Part I. 
I Ibid. 1837, Plate II. 
t Ibid. 1836, Plate XXVII. 
§ Ibid. Plate III, 
