29 3 Dr, Blag den’s Experiments on 
part of the fcale in thofe which have a greater effect, this pro* 
grefiion may be infenfible, or be incapable of determination by 
fuch experiments as thefe, which by their nature do not admit 
of extreme accuracy.; but it may become fufficiently obfervable 
toward the laft additions of fuch lalts as are foluble in great 
quantity, and fuch as alter very much the freezing point. I 
never fucceeded to freeze the faturated folution of this Bor- 
rowftounnefs common fait, though it has been cooled feveral 
degrees below — 4 0 without depofiting any of its fait ; if the 
experiment were made in a cold fufficient for the purpofe, it 
would fhew whether any irregularity takes place in the a&ion 
of this fait upon fnow, or whether fuch a decreafing ratio 
does exift. Perhaps, however, the whole may depend upon 
the principle alluded to formerly, that the prefence of fome 
fait favours the depolition of more : for when a fait is mixed 
with fnow, it may in this point of view be conlidered as in 
the fame jjate with a faturated folution of the fait which has 
fome of it remaining undilfolved ; and which, therefore, will 
not contain more than properly belongs to it at the given tem- 
perature ; and the cold of fuch a frigorific mixture Ihould be 
no greater than that of the freezing point of the faturated fo- 
lution under thofe circumftances. 
As it is well known that water, after it has been faturated 
with one fait, will take up a certain portion of another fait 
without depofiting any of the former, I was curious to try 
what effect the addition of this fecond fait would produce on 
the freezing point ; and particularly whether it would deprefs 
the freezing point of the faturated folution the lame number 
ol degrees that an equal proportion of the fame fait would 
deprefs the freezing point of water; and whether the fame 
fimple 
