'The Transactions of the Bombay Geographical Society. From January 1863 to December 1864. (Edited by the Secretary.) Volume XVII.' [‎78] (107/524)

J xxv {ii PROCEEDINGS of the
places before the wave arrives, and the tidal wave is travelling at the
rate of one thousand miles per hour, when high-water is only moving
from twenty to sixty. I compare it to a single vibration produced by
the original wave coming in contact with the chops of the channel;
here we have a horizontal instead of the original vertical force, and I
think it is easy to understand why certain winds should cut it both i n
height and time, and the converse.
The Rev. Samuel Haughton states, that the rise is so little for many
minutes before high-water, that the eiror tor calculation in question is
inappreciable, and in a note from his friend the Rev. George Gage,
Proprietor and Rector of Rathin Island, that the mean range at Church
Bay on that Island is from three to four feet (full and change), but that
in stormy weather, its extreme range is from nine feet to two inches,
according to the direction of the prevailing wind.
I think that London is a bad standard for determining the times of
high water, Brest or Dover would be better, but perhaps the best place
is to be found on the coast of Australia.
*****
By your next meeting I hope to give a photograph and description
of the Magnetimeter, by which I think the Geographical position of a
ship at sea can be estimated with tolerable accuracy without astronomical
observations.
I remain, dear Sir, yours faithfully,
T. Wherland
To the Secretary Bombay Geographical Society.
“Tudor” Bombay, 2\st May 1863.
Dear Sir, —Enclosed is a description of the Magnetimeter, which
model I believe to be original. The observations speak for themselves,
and making due allowances for the rude way the instrument is got up,
will give it a fair valuation.
If I am too enthusiastic in saying it may aid in determining a ship’s
position, still the experiments from such an instrument will be of value
and interest, in showing the everchanging magnetism of the soft iron in
ships going north and south, and consequently the variation in quadren-