276 
Monpay, DecemBer 10TH, 1855. 
REV. SAMUEL HAUGHTON in the Chair. 
Tue Rev. Joseru A. GALBRAITH made a communication on 
the subject of the barometric measurement of mountain 
heights. He laid before the Academy the results of ten 
measurements of the height of the Two-Rock Mountain, 
made by Professor Haughton and himself during the years 
of 1853, 1854, 1855, with the view of settling some dubious 
points connected with the use of the barometric formula. They 
commenced operations by measuring with the staff and level 
the exact height of the summit of this mountain above the floor 
of the magnetic observatory in the Fellows’ Park, Trinity 
College. This height they found to be 1738-63 feet. With 
this standard Mr. Galbraith compared the heights calculated 
from the different barometric formule which have been pro- 
posed. ‘The formule he computed from were as follows : 
. 0 h 
I. H (in fathoms) = € + 75) 10000 x log 7. 
This is the formula commonly used in this country; 0 
being the mean temperature of the column, reckoned from 
32°. In this formula no account is taken of the hygrometric 
condition of the air. 
6 h-f 
IL. H-(14 i) 10000 x log =. 
In this formula, which was proposed some years ago by 
Professor Apjohn, fand / are the observed tensions of aque- 
ous vapour at the two stations. 
2 0 Sie 
Il. H-(14 gp) 10000 «log = a 
A 
