measuring Heights with the Barometer . 723' 
was always made ufe of, I fhall annex to this paper, a 
plan of the triangles and detail of the operations for ob- 
taining the height of Snowdon; becaufe that mountain, 
at the fame time that it is the higheft I have meafured, 
is, from its fituation, more likely to be vifited, and to 
have experiments repeated upon it, than the remote hills 
of the North. I now proceed to give fome account of 
the barometrical obfervations. 
The heights in and near London being fo very incon- 
fiderable, it was eafily forefeen, that nothing conclufive 
could be drawn from obfervations made on them alone. 
It was, however, natural enough to try, even on thefe,, 
whether the rule we had been furnifhed with would an- 
fwer? A fmall height of 41 feet 4 inches, which, with- 
out inconveniencv, could be recurred to at all times of 
the day, and all feafons of the year,, was the firft that 
%vas made ufe of. St. Paul’s, Hampftead, Kew pagoda, 
and Shooter’s-hill, were the next. The mean refults of 
many obfervations on the three firft, and of feveral on 
Shooter’s-hill, were found to be defective. In general 
the coldeft obfervations, made in the morning and even- 
ing, when the temperatures at the two ftations differed, 
lead from each other, anfwered bed. In the hotted part 
of the day, when that difference was the greated, the 
refults were nioft defective. 
Some 
