[ 5 ii ] 
AN ACCOUNT, &c. 
I T is at prefent well known, that by the evaporation of va- 
rious fluids a fenfible degree of cold is produced ; and that 
by the evaporation of ether, which is the mail volatile fluid 
we are acquainted with, water may be congealed, and the ther- 
mometer may be brought feveral degrees below the freezing 
point. But as various thermometricai experiments, wdiich I 
lately made, have exhibited fome new phenomena, and as I 
have contrived an eafy and pleafing method of freezing a fmall 
quantity of water in a fhort time, and in every climate ; I 
think it not improper to give an account of thefe things in the 
fir ft part of this lecture. 
My firft experiments were intended to difcover, if poftible, a 
fluid cheaper than ether, by the evaporation of which a 
degree of cold fufficient for fome ufeful purpofe might be 
generated. But in this my expe&ation was diiappointed, as 
I found that ether was incomparably fuperior to any other 
fluid, as the cold it produced was feveral degrees greater 
than that occafloned by any other of the moft volatile fluids 
whatever. Being, therefore, obliged to ufe ether, I en- 
deavoured to contrive a method, by which the leaft poftible 
quantity of it might be wafted in the production of a degree 
of cold fufficient to freeze water, and in this I met with fuc- 
cefs. But before we come to the defcription of this method, I 
Vol. LXXI. X x x fhall 
