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THE REV. W. WHEWELL ON TIDE OBSERVATIONS 
The amount of the semimenstmal inequality of height also varies. In general the 
greatest range, as will be seen by Table X., is twice or twice and a half the smallest ; 
but this rule is far from universal. And many of the cases which appear to approach 
to this rule, really deviate from it when allowance is made for the diurnal inequality. 
Thus on the coast of America, Mount Desert Island, the whole amount of the semi- 
menstrual inequality of high water is about three feet in a tide of thirteen feet, thus 
reducing the smallest range to eleven ; but the diurnal inequality reduces it further 
to eight feet. 
The column headed ££ Mean” in Table XI. exhibits not only the amount but the 
law of the semimenstmal inequality of the heights, so far as it is given by the obser- 
vations of June 1835. It is not likely, however, that so short a series can be of much 
value for this purpose. 
Sect. VII. General Remarks, and Tables . 
30. The preceding are the principal conclusions which offer themselves as resulting 
from the tide observations of June 1835. I trust that they will be considered of some 
value, especially when taken in connexion with the further researches to which they 
direct us. The form of the cotidal lines, and the progress of the tide-range in going 
along the shore, are points of considerable interest ; but perhaps the most important 
consequence of this investigation is the prominence it gives to the diurnal inequality. 
We have here a regular change of the height of the tide, which in many places is not 
less than the difference of spring and neaps, which operates every day, but which has 
never yet been introduced into tide tables, and of which the law is not yet precisely 
known. It is of great importance, both to the theory of the tides and to the purposes 
of navigation, that this diurnal inequality should be fully analysed. The perplexity 
produced by the difference of its epoch on the coasts of America and of Europe, may 
perhaps be removed by the examination of observations at intermediate places. With 
this view I shall, as soon as I have the means, discuss observations made at Bermuda, 
and at Halifax in Nova Scotia ; and it would be of use also to have observations at 
Iceland, at the Cape of Good Hope, and on the coast of Africa. It may be observed 
that observations would be available for this purpose if they gave the height of high 
water merely, without the time, a kind of observation made with little difficulty and 
trouble. 
31. I shall now give a list of the Tables and Maps which are the results of the 
series of tide observations of June 1835, according to the preceding discussions. 
Tables I. to IX. The correct establishments and cotidal hours of the places at 
which the most useful observations were made in June 1835. 
Several sets of observations have been omitted in this list, not because they were 
less carefully or skilfully made, but because on various accounts it was not desirable 
to combine them with the others. 
