£20 Mr. cav allots Account of 
fo diftil the ether from it, which muft come fufficlently pure 
for common ufe. 
It is commonly believed, that water combines with the pureft 
part of ether, when thofe two fluids are kept together; 
whereas, by the above defcribed procefs, the contrary is efta- 
blifhed : perhaps when ether is kept in contact with 
water for a long time, the pureft part of it may appear to 
be loft, becaufe the ether may bs combined with, and may 
retain fome water in itfe.lf, at the fame time that the water 
combines with and retains fome ether, whereas the cafe may be 
different when the ether is quickly waffled in water, and is im- 
mediately after feparated from it : but in refpeCt to this I have 
yet not made any experiments, fo as to be able to decide 
the matter. 
II. Experiments relating to the expanfon of mercury . 
THE difficulty and uncertainty attending the various me- 
thods hitherto propofed for inveftigating the expanfion of quick- 
filver, or its increafe of bulk when rarified by a given degree 
of heat, determined me to contrive fome method by which 
this purpofe might be effected with more certainty and preci- 
fion. After various experiments I hit upon the following me- 
thod, which to me feems both new and capable of great accu- 
racy, though in this I may be deceived. 
Firft, having blown a ball to a capillary tube, fuch as are 
commonly ufed for thermometers, I weighed it, and found that 
this empty thermometer was equal to 79,25 grains. This 
^empty glafs previous to its being weighed was rendered as per- 
fectly 
