ot es 
inftance, vegetables, calcarious ftones 
nitre, &c. That a fluid body may 
become a folid, is nothing extraor- 
dinary ; we fee that water becomes 
as folid as a ftone, and remains fo, 
in a place fufficiently cold. There 
are perhaps in the world no fub- 
tances which are by their nature 
fiuid: for all fab{tances yet found 
may be, by different operations, 
principally by a fufficient degree of | 
heat, rendered fluid; and all fluids 
may be changed into folid bodies 
by applying to them a fufficient 
degree of cold. Mercury itfelf was 
rendered as malleable as any other 
metal, by Profeflor Brown at-St. Pe- 
terfburg, by a very great degree of 
cold. et 
Since that kind of air is known, 
which goes now under the name 
of fixed air, and which Van Hel- 
THON 
