678 Col. roy’s Experiments for 
whereby the vacuum was deftroyed in fo remarkable a 
degree. Since this accident made it neceffary to reboil 
the quickfilver, the water (then between 1 8o° and 1 90°) 
was let out by the cock fixed for that purpofe at the 
bottom of the veflel; but before it could be intirely 
drawn off, the tube and its contents, had fo fenfibly felt 
the condenfing force of the furrounding atmofphere, 
then about 48°, that the quickfilver had rifen again, and 
prefented itfelf oppofite to the eye of the veflel, fome- 
thing lower indeed than where it formerly flood. On 
this difcovery, and as foon as water could be boiled for 
the purpofe, the veflel was filled again, when the quick- 
filver fubfided, as before, quite out of fight ; and on draw- 
ing off the water a fecond time, it rofe anew, feemingly to 
its former height. 
The appearance, which this accidental circumftance 
produced, was fuch, as naturally fuggefted that farther 
experiments might have been made, varied as much as 
pofiible from each other, by the admiflion of different 
quantities of air, or of air and moifture intermixed. But 
the nature of the vefiel rendering it impoflible to fee, 
and confequently to meafure, the motion of the quick- 
filver, occafioned by the alternate expanfion and conden- 
fation of the elaftic vapour contained in the upper part 
of the tube, and which could not have been accom- 
plifhed 
