194 Mr. Wollaston's description of the 
above the foot pavement on the north side of St. Paul's 
church-yard, and boiled again in the Gilt Gallery, there was 
a difference of 254 parts, barometer being 29,92, thermo- 
meter 77. 552 parts: 530 feet :: 254 parts : 243,87 feet, to 
which add the correction by Roy's table of the height 
= 28.77, and the corrected height is 272.64. General Roy 
makes the gallery above the north pavement to be 281 feet, 
which allowing 4 or 5 feet for the difference of our lower 
stations, would give 266 or 267 feet for my observed height, 
differing only by about 4 feet. If I take my proportion from 
Roy’s statement that i° Fahrenheit = 535 feet, the result will 
be still nearer. 552 : 535 : : 254 : 246,1 , add correction 
29, the corrected altitude will be 275,1 feet, differing less 
than 2 feet. 
One other observation I made with the same thermometer 
on a height ascertained also by General Roy. My thermo- 
meter boiled at the ferry-house, opposite Woolwich arsenal, 
stood at 869, and in the Prospect-room at the Inn on Shooter's 
hill, it showed 432, a difference of 437 parts, barometer 29,94, 
thermometer 58. 
552: 530: -.432: 419,6^ 
. . 67,5 0 V height corrected = 447,9. 
Add correction = 28,3V 5 
IOOO J 
By Roy, the height from the Gun wharf at Woolwich to the 
upper story at Shooter's hill is 444 feet. 
If this instrument should be thought deserving of being 
brought into use for scientific purposes, the sensibility and 
length of the thermometer would be selected by each person 
according to the particular object in view. With a sensibi- 
lity equal to that of a common barometer, i° of Fahrenheit 
