( *J3) 
linder of Mercury ; for {{Mercury be more expanded, and 
confequently lighter in warm Weather than in cold, it 
will neceflarily follow, that the fame weight of Atmo- 
fphere will require a taller Cylinder in Summer, and a 
ihorter in Winter to counterpoife it. And if the Ex- 
tremity of Weather do but occafion an 150th part dif- 
ference, as 'tis probable it doth, the effed thereof on a 
Barometer will be a tenth of an Inch above and below 
the Mean, or a Fifth in all. 
III. I fill'd the fmaller Bolt-head with Spirit of Wine, 
and having fet it in the Skillet of Water over the Fire, I 
found that it afcended gradually as the Heat encreaied, 
but flower at firft, and fafter after it was well warm. At 
length being arrived at a certain degree of Heat, it 
would fall a boiling with great Violence, emitting Bub- 
bles, which coming into the Neck of the Bolt-head, 
w r ould lift all the Incumbent Spirit, till they had made 
their way through. And thefe fucceeding one another 
very faft, would often raife the Spirit to the top of the 
Neck, and fpillit ; fo that I found I could go no fur- 
ther with this Liquor, than to that degree of Heat which 
occafion'd this boiling, and which wanted very much of 
that of boiling Water, being almoft tolerable to the 
Touch. It was however very remarkable how exactly 
this degree of Heat was determia'd by the expanfion of 
the Spirit, for in the inftant it reached a certain Mark on 
the Neck, it began to emit its Bubbles : and having been 
taken out a little to cool and fubfide, it w r ould certainly 
and conflanriy fall a bubling again, when upon a fecond 
Immerfion, it was arrived at the aforefaid Mark : During 
this Experiment, it appeared both by the Dew on the 
Neck, and by the Scent in the Room, that tho* the Neck 
were about 30 Inches long, yet the Spirit did evaporate 
very faft for the fmallneis of the Surface of the Liquor 
And I have often noted the like Evaporations condenfed in 
L z Dew 
