228 
MR. LUBBOCK ON THE TIDES. 
XX., and XXI., is more striking for the heights than for the intervals. This, I ap- 
prehend, is partly owing to the circumstance that the corrections for the height vary 
but little with the moon’s age, and are therefore less influenced by the particular 
moon’s transit chosen to be the argument of the tables. 
In future, for the port of London, the phenomena of the tides may safely be pre- 
dicted by employing tables founded on Bernoulli’s theory, having for their argument 
the fifth transit of the moon preceding the high water of which the time and height 
are required, and founded upon the constants (A), D and (E) given in pp. 223 and 
224. Such tables are included in those contained in this paper, and calculated by 
Mr. Jones, which give the comparisons between theory and observation. The calendar- 
month correction is of course to be considered as included in those for the declina- 
tions and parallaxes of the luminaries. 
In estimating how far the agreement between theory and observation is to be con- 
sidered as complete, it must be recollected that it is impossible, even with the appa- 
ratus at the St. Katherine Docks, to determine the exact minute of high water ; for 
the water almost always continues stationary for some time, without falling one tenth 
of an inch. At the London Docks they only attempt to register the time to the 
nearest five minutes. 
Mr. Peirce informs me that he cannot account for the difference between the obser- 
vations at the London and the St. Katherine Docks. The swell of the steamers cannot 
affect the gauge at the latter place, as it is completely sheltered from any motion of 
the surface of the river. I suspect occasional errors of transcription, particularly 
in the month of January last. Results of theory cannot offer a closer agreement 
with those of observation than observations at the same place, or at places separated 
by a short distance, do with each other. Tables A and B, which have been furnished 
me by Mr. Deacon, offer a comparison between the observations at the London and 
at the St. Katherine Docks. The observations have been brought up to the same 
standard by the addition of certain quantities ; in order that if no source of error 
existed, they might present no difference. 
The tables in this paper having reference to the interval between successive transits 
of the moon, furnish the means of shifting the argument approximately. 
