DIURNAL INEQUALITY WAVE ALONG THE COASTS OF EUROPE. 
233 
some of the facts do appear to indicate this farther irregularity. For example, the 
diurnal inequality appears sometimes, for several days, to leap from its proper tides 
to the alternate tides, without vanishing* in the transition, as in rule it does. Now 
this irregular movement may be accounted for by supposing- that the diurnal wave, 
which usually completes its oscillation and returns in twenty-four (lunar) hours, does 
sometimes occupy a longer or shorter time in the oscillation. If, for instance, this 
wave, after arriving four hours before the superior high water of one day, arrive 
again twenty hours afterwards and therefore eight hours before the superior tide of 
the next day, it will be only four hours after the inferior high water of the second day; 
and therefore the diurnal inequality will pass from the superior to the inferior tide 
by a leap. There appear to be several cases implying a change of this kind, but the 
subject is so complex and so laborious that I shall not now pursue it. 
I venture to observe, that what has been recently done in the prosecution of our 
knowledge of the tides, proves the claims which it has for the same kind of attention 
and support which is given to other branches of astronomy. The immense labour of 
following out any one portion of this subject may be judged of, from a very slight 
attention to any part of the researches of Mr. Lubbock and myself upon it. In the 
present memoir I have selected the best-conditioned and most carefully made obser- 
vations out of the general mass of those made in June 1835. I have had the curves of 
high and low water drawn for seventy-one such places. From among these, I have 
taken the nineteen places mentioned in this memoir, and have caused the diurnal wave 
curves to be tabulated and drawn, of which a series is represented in the diagram. 
These calculations and diagrams have been performed by Mr. D. Ross of the Ad- 
miralty, without whose services, placed at my disposal by the First Lord of the Ad- 
miralty, it would have been impossible for me to proceed. And even with all the 
assistance which can thus be given, the superintendence of the subject of the tides 
alone might fully employ one man of science, with great advantage to the progress 
of our knowledge ; the subject being now so far opened that it is pretty clear in 
what manner research may be profitably pursued. 
There is another reason why tide investigations should be made a national work 
in civilised maritime states. The peculiarities of the tides in each country are such 
as to make each shore a study by itself, and our best generalizations will be collected 
from results obtained in separate parts and combined. I have given less of my labour 
to the coasts of the United States of North America than might have been due to the 
interest of the tides of that part of the Atlantic, because I was obliged to limit my 
labour in some direction, and I hoped, and do hope, that the subject will be taken up 
by the government of that country as well as our own. 
Suffolk Street , 
June 15, 1837- 
