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XL Researches on the Tides. — Fourteenth Series. 
On the Results of continued Tide Observations at several places on the British Coasts. 
By the Rev. W. Whewell, D.D., F.R.S. 
Received October 24, 1849, — Read January 31, 1850. 
Tide observations made at several different parts of the British and the neighbour- 
ing shores, and in some instances continued for a considerable period, have been 
discussed by Mr. D. Ross of the Hydrographer’s Office, with great labour and per- 
severance ; and as the results which his labours afford may be of use to mariners, I 
offer to the Royal Society a brief statement of these results. 
The discussions at present referred to relate to the height of high water, and the 
variations which this height undergoes in proceeding from springs to neaps and from 
neaps to springs. It is found, by examining the observations at 120 places and throw- 
ing the heights into curves, that the curve is very nearly of the same form at all these 
places. Hence the semimensnal series of heights at any place affords a rule for the 
series of heights at all other places where the difference of spring height and neap 
height is the same. For instance, Portsmouth, where the difference of spring height 
and neap height is 2 feet 8 inches, is a rule for Cork, 
Waterford, Inverness, Bantry, Boucout on the 
French coast, and other places. 
And the Tables of the height of high water at 
one of these places suffice for all the others, a con- 
stant being of course added or subtracted according 
to the position of the zero-point from which the 
heights at each place are measured. 
The series of heights of high water for a semi- 
lunation also agrees very exactly, as to the form of 
the curve, with the equilibrium theory. The follow- 
ing construction gives this curve. 
With centre C and radius CA (half the difference 
of the height at spring and neaps), describe a circle; 
and in AC produced take CD to CA as 12 to 5. 
Divide the circumference of the circle into twelve 
hours, representing the twelve hours of moon’s 
transit ; and join D with each of these divisions. 
The lines thus drawn to the hours will give the 
heights of high water for each hour of the moon’s 
2 G 2 
