in order to af certain the height of Mountains. 559 
by preifure during the experiment; and this effeCt may- 
be prefumed to have been the moil fenfible, when the 
veil'd was filled with water, the preifure at that time 
being from within. To alfure myfelf of this, I let in a 
fmall quantity of air, which formed a bubble of about 
one-third of an inch in diameter, and upon immerging 
the glafs in another veifel of water, whereby the pref- 
fure within was counterpoifed by a preifure without, the 
bubble feemed, to contrad itfelf by a quantity, as I found 
afterwards, equal to about tyro grains in weight, or — ^ 
of the whole contents. I therefore concluded, that this 
correction was hardly worth taking notice of, and ftill 
lefs the effeCt from external preffure when the glafs was 
exhaufted. At every operation the height of the baro- 
meter and, thermometer (placed clofe to the veffel when 
the air was weighed) was noted down, together with the 
height of the pump-gage, which, compared with the 
barometer in the room, fhewed the quantity exhaufted. 
The refult of the experiment was as follows, the baro- 
meter in the room Handing at 29.27 inches, and the . 
heat of the room 53°. 
The • 
