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A P P E N D I X .
In the second CIHSS we considered aU the minor fixed points
which were included in the triangulation, excepting the details of the
coast, and • boundary lines,'* which belonged to the third class.
We supposed that the ship had saUed from the ' first' harbour.f At
six. in the morning, (marked 6) the position of the vessel was fixed
by two or more angles between marks, iûready fixed, upon the land.
At 6-30, and at 7 similar means were used to fix the slup's place.
Soundings were talsen, and laid down by proportioning to the times
of each sounding, the portions of distances run between the two
stations, as shewn by patent log, by bearings of a mark, such as
e (in the figure) wliile saihng from 6'30 to 7 : by independent
double angles, (two angles between three marks), or by simple crossbearings.
Transit bearings were always sought for, by compass as well as by
noting when marks were ' on ;' or, in ahne, one with another, without
reference to the compass. We endeavoured to ascertain (or fix)
the sliip's position at the same moment, by the most available of the
numerous methods so readUy occurring wliile the log was going, the
time noted carefully (as often as angles or bearings were taken),
and several first class marks in sight. Transit bearings were useful
in the details of the coast line, as may be seen by the lines drawn
from 6-30, 7 and 8 ; and they corroborated the correctness of the
triangulation, when applied to first and second class marks.
By a judicious selection of objects, and a clever apphcation of
transit bearings, I have seen extensive and correct triangulations
carried on from data, obtained at sea, which appeared utterly inadequate.!
I do not imply that the absolute position of any one
point was independently correct, because all depended at first upon
obsen'ations at sea ; but that the points of the triangulation were all
so correct, relatively, that, upon after examination, when the regular
routine of harbour work had been combined with the data obtained
afloat, and their truth ascertained by connection with the previous
observatory, no alteration was found necessary.
Perhaps I should explain, that in the plan of the ' first ' harbour
all depended upon the base Ab ; by which also were fixed B and C.
From the summits B and C ; — G , D, E, F, were fixed, as well as a
• By ' boundary lines ' I mean limiting outlines of shoals, or rocky
t See figure. J By Mr. Stokes.
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