54 
MR. LUBBOCK ON THE TIDES. 
lieve to be attributed to the imperfection of the observations than to the inac- 
curacy of the Tables. The time is only recorded in the Dock books to the 
nearest five minutes. 
The Committee of the Astronomical Society, to whom the improvement of the 
Nautical Almanac was referred, having recommended the insertion in that work 
of a “ Table of the mean time of high water at London Bridge for every day 
in the year, and also at the principal ports at the time of new and full moon,” 
(see Report of the Committee of the Astronomical Society relative to the im- 
provement of the Nautical Almanac, p. 14,) — without doubt that accuracy will 
be introduced into these calculations which has long been applied to all other 
astronomical phenomena. 
In the open ocean the rise of the tide is so small that it is difficult to fix the 
time of high water, and the effect of the wind is so capricious, that it seems 
difficult to do more than to determine the establishment of the port ; to which 
the mean of all the times of high water observed at any point of the lunation, 
will in this case afford a sufficient approximation. When this constant has 
been obtained at many places on the surface of the globe, the march of the 
great tide-wave will be ascertained, the numbers given on the map drawn by 
Mr. Walker, and which accompanies my former paper on this subject, maybe 
rectified, and many anomalies which it now presents will no doubt disappear. 
In narrow channels and archipelagoes the case is widely different : here the 
moon’s age and even her parallax and declination have a perceptible influence ; 
and if accuracy be required, all these circumstances, together with the period 
of the year, must be taken into account. 
The observations which already exist would, if carefully discussed, furnish 
the means of determining the establishment of the port (X t ), the fundamental 
hour of the port (A), and the constant which contains implicitly the 
mass of the moon throughout the British Isles, and probably in many other 
places, as along the coast of France, at Madras, &c. * Having obtained these 
constants, Tables might be constructed, which by merely adding a given quan- 
tity would be sufficiently correct practically for a considerable extent of coast. 
These constants have been determined for the London Docks, and for the 
* As is done in this paper for Brest. 
