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PHIPPS’S JOURNAL, 577
of the mountain was then taken with the vertical arch, as a means of detecting any error
in the obfervation, and was found to be 8° 50’. The diftance not enabling me to take
the depreffion of any particular part of the ftaff by the fea-fide under the land on the
other fide accurately, I fent a man to ftand clofe before it, and took the depreffion nearly
to his eye, which was found to be 1° 54’. The inftrument was then removed to the
ftation on the right (B). The inftrument being adjufted with the fame precautions as
before, and the fixed telefcope pointing to the center ftation (A); the angle to the
mountain was 84° 58’, the angle to the ftation by the water-fide(C) 294° 44’. The
inftrument was then removed to the {tation by the fea-fide (C), the fame precautions
ufed in adjufting, and the fixed telefcope pointing to the center (A) in one with the
mountain, the angle to the ftaff on the right (B) was 24° 44’ Intending to make the
triangle BCD ifofceles, and imagining there might be fome little error from the uneven-
nefs of the ground, I fet off on the theodolite an angle equal to the laft, having a perfon
ready with a ftaff on the bafe line to fix it where that angle fhould interfec& on looking
through the telefcope ; I found it cut exactly at the ftaff D 335° 16’, and from thence con-
cluded the meafure of the bafe to be exact. I then took the altitude of the mountain
by the vertical arch 7° 44’.. I then removed the inftrument to the {tation (D) to take
the third angle ; but from the badnefs of the ground, I could not place the inftrument
exactly over the fpot where the ftaff ftood; from hence I took the third angle of the
triangle; the fixed telefcope pointing to (A), and the fame precautions of adjuftment
being obferved, the angle to C came out 65° 15/; lefs by one minute than it fhould have
been. I then took from the fame place the angle to the mountain (FE) 275° 1’; more
by one minute than the correfponding angle at the oppofite {tation (B): but the errors
correcting each other, the whole angle C D E = 150° 14’ = the whole angle CBE.
By the triangle ABC, AC comes out 1771,4 feet :
By the triangle ABE, AE comes out 9265,0 feet :
Therefore the diftance CE is - 11036,4 feet.
Angle of the mountain’s elevation feen from C 7° 44’:
Height of the mountain above C - 1498,8 feet:
+ height of C above the water’s edge me
Height of the mountain above the water’s edge 1503,8 feet.
I prefer this obfervation to the others, becaufe the three angles of the triangle ABC
came out exactly 180 degrees by the obfervation. The diftance AC found by the
computation, differed only four feet from that by the meafure; but, the ground being
uneven, I did not depend upon the meafure, but took it merely as a check upon the
operation, to detect an error, in cafe of any great difference.
The diftance found by the fimilar triangles BC E and CD E comes out 11037 feet ;
The angle of the mountain’s elevation feen from A was 8° 50’;
Hence the height of the mountain above A was found = - 1439,8 feet :
Depreffion of C feen from A was - . nn 5403
Hence the height of A above C is - - - 58, 7 feet ;
Height of the mountain above C - - - 1498,5 feet :
+ height of C above water’s edge . - - oa
Height of mountain above the level of the fea - - 1503,5 feet ;
which differs from that found by the fingle angle three-tenths of a foot.
I cannot account for the great difference between the geometrical meafure and the
barometrical one according to M. De Luc’s calculation, which amounts to 84,7 feet. I
have no reafon to doubt the accuracy of Dr. Irving’s obfervations, which were taker
with great care. As to the geometrical meafure, the agreement of fo many trianeles,
VOL. I. AE each
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