'The Transactions of the Bombay Geographical Society. From January 1863 to December 1864. (Edited by the Secretary.) Volume XVII.' [‎9] (170/524)

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Art. II.— Further Discussion of the Tidal Observations made for Go
vernment at the Colaba Observatory in 1861.—By J. Burgess,
Esq., F.E.I.S.
[Read before the Society, February 19th, 1863.]
At the last meeting of the Geographical Society, I read a paper on the
value of Professor Orlebar’s formula, as applied to the prediction of the
Bombay tides, founded on the relations between the means of the
computed and observed times of high-water at the Colaha Observatory
in 1861. From theory, and from the alterations that have taken place
in the harbour within the last 15 years, it was to be inferred that the
formula, founded on a comparatively small number of observations,
could not now be counted upon as sufficiently accurate. The paper
was based upon the natural assumption that the formula was at fault,
and that the observations recorded and published were generally trust
worthy. Want of time prevented my examining them any farther
than determining the algebraic sum of the differences between the
observations and computed times, which happened to amount only
to about 10 minutes. Certain observations I did suspect to be con
siderably in error, but it is only since the meeting, and in consequence
of remarks then made by Lieutenant Fergusson, the Government
Observer, and Captain Barker, the Master Attendant, that I have
examined the observations individually—with what results will imme
diate!}^ appear.
I may however premise, that it was my intention to determine the
constants in the formula necessary for representing the times of high-
w ater for 1861, by which to test the accuracy of the observations. Not
having full confidence in the values of the constants mentioned in my
former paper, and which were derived almost solely from the observations
at or near the syzygies, I attempted to determine x the ratio of the lunar
and solar effects, and y the moon’s elongation from the sun at the time
of the highest tide from the intervals between the moon’s transit and
high water at each hour. This gave me twelve equations of the form—
x sin A—sin (B—A) cos 2 ?/ + cos (B—A) sin 2^ = 0
I