the Point oj\Cong elation, ^ x 
made by diluting the fame acid with different proportions of 
water. 
* 
I fhall conclude this Paper with the account of an experi- 
ment to determine the effect of fait upon the expanfion of 
water by cold. Pure water begins to {hew this expanfion about 
the temperature of 40°, that is, 8 degrees above its freezing 
point. 1 put a folution of common fait, in the proportions of 
4»8 parts of water to one o'f the fait, and confequently whofe 
freezing point was 8°§, into an apparatus I had ufed for other 
. experiments of the fame kind; and found that the folution 
continued to contract till it was cooled to 17 0 , but had fenfibly 
expanded by the time it was cooled to 1 5 0 . Suppofe the expan- 
lion to have begun at i6°§, it would be juft 8 degrees above 
its new freezing point. Hence we have reafon to conclude, as 
far ns one experiment goes, that the combination of a fait 
with water has no other effefl upon its quality of expanding 
by cold, than to deprefs the point at which that quality be- 
gins to be fenftble, juft as much as it depreftes the point of 
congelation. 
It is probable, that the fubjefl of this Paper will appear to 
foine minute and trifling. 'Did it lend to nothing further, that 
opinion might be juft. But it is by the accumulation of fa£b 
of this kind, and efpecially fuch as have been developed by 
Mr. Cavendish in his excellent Papers on the freezing of 
acids *, that the foundation muft be laid for a general theory 
of the laws of cohefion, which may ultimately lead to a know- 
ledge of the ftru&ure upon which the intimate properties of 
* Philofophical Tranfa&ions, Vol. LXXVI. p. 241. and p. 166. of -this 
Volume. 
bodies 
