"معاملات الجمعية الجغرافية في بومباي. من يناير ١٨٦٣ حتى ديسمبر ١٨٦٤. (تحرير السكرتير.) المجلد XVII." [‎١‎٦] (٥٢٤/١٧٧)

16
REMARKS ON THE
the tide is admitted generally to be affected by it [i. e. the wind] i n
some way, but it is matter of doubt, whether the time of the tide, or
rather the velocity of the tide waves, is at all affected. M. Daussy
denies the existence of such an effect in the French observations, while
it has been found by Mr. Lubbock in the London tides and again at
the conclusion of the same report they add— u It is difficult to deter
mine whether the wind produced a decided enect on the velocity of
these tides. By a discussion which was attempted, it appeared that
on all the days in which the easterly wind prevailed, compared with all
the days in which the westerly wind prevailed, there was a difference of
one minute more and of one minute less than the mean ; the tide being
accelerated by the coincident wind and retarded by the opposing one.”f
Hence it would seem, that the error in the times of the Bombay
tides, attributed to the wind, must, to a large extent, be due to
the method of computation, and that this part of the error would
disappear if the observations were made with sufficient care to enable
us to determine the mathematical expression representing them. This
careful observation, however, appears to have given Lieutenant Fer.
gusson no anxiety; he considers that “ all that is required, 35 is to
obtain the time “ with sufficient accuracy for practical or nautical
purposes. 55 Now, if this be all that is desired, it seems to be
quite unnecessary for the Government Observer to continue his im
perfect observations, seeing, as he says, he can predict the time of
high-water with this degree of accuracy from the Nautical Almanac.
But surely higher purposes are to be served and for which a cycle of
accurate observations made at Bombay might be of the greatest value.
The tides are still an interesting subject of scientific research.
Mr. Haughton is at present engaged in reducing the observations
made in the Arctic Ocean, and the same physicist has advanced our
knowledge by the separation of the solar and lunar effects. It is,
indeed, actually found at some ports—as Air. Airy first pointed out
in the case of Courtown in Ireland—that the solar tide is greater than
the lunar one. Again, it is well known that at certain phases of the
tide it rises or falls in some harbours more in ten minutes than at other
phases it does in an hour. In such cases it is evident that an error
of even small amount may be of considerable consequence even to
British Association Reports, 1837, page 420. -
t Id. p. 463 0