394 
MR. LUBBOCK ON THE TIDES IN THE PORT OF LONDON. 
posed to be included in the angle l t : this result is directly contrary to obser- 
vation, as may be seen by Table VIII. This difficulty may be got over by sup- 
posing the coefficients (C) of the angles 2 6 t — 2 \ — l t and 2 6 t — -f to be 
different ; it remains however to assign the cause of this difference. 
Not having been able to satisfy myself with respect to this and other discre- 
pancies, I shall not attempt to form any Tables from theory for the purpose of 
calculating the effects due to changes in the declination of the luminaries, and 
in the parallax of the moon; but I hope that no great length of time will elapse 
before the results contained in M. Dessiou’s Tables will be confirmed by more 
accurate observations here and elsewhere, and that the problem of the tides 
will meet with the attention it deserves, no less practically than in connection 
with Physical Astronomy, and particularly with the determination, even if im- 
perfectly, of the mass of the moon. “ Les marees ne sont pas moins interes- 
santes a connoitre, que les in6galites des mouvemens celestes. On a neglig£ 
pendant long-temps de les suivre avec une exactitude convenable, a cause des 
irregularity qu’elles presentent ; mais ces irregularity disparaissent en mul- 
tipliant les observations.” — Exp. Syst. du Monde, p. 289. 
The Tables XV. XVI. &c. present irregularities, owing to the comparative 
paucity and the imperfection of the observations. M. Dessiou has therefore 
formed Tables from these, in which these irregularities are arbitrarily removed : 
these Tables are published in the Companion to the British Almanac for 1832, 
and no doubt represent the phenomena rather better than the former. As, 
however, these alterations are arbitrary, I have preferred giving here the re- 
sults of the observations without any change. The observations employed were 
taken in all cases indiscriminately from the Dock books. 
I have now only to express my acknowledgements to the Committee of 
the Society for the Diffusion of Useful Knowledge, and to Mr. Pond the late 
superintendent of the Nautical Almanac, who have given me M. Dessiou’s 
assistance in forming the annexed Tables. 
