the Point of Congelation . 28; 
flirred with any force, the remaining nitre depofited itfelf in 
fuch minute cryltals as to have much the appearance of a 
powder; I fuppofe from the deftru&ion of the regular furfaces 
upon which it would otherwife have continued to form. 
Frequently, in the stronger folutions, there appeared neat 
the bottom and fide of the tumbler many elegant debated 
crydals, perhaps a quarter of an inch in diameter, all fepa- 
rate, but fometimes crowding very clofe upon one another, fo 
as to exhibit a fpe&acle of much beauty. 
The ice of folutions of nitre, efpecially when it began to 
thaw, was very different from common ice, having a foft 
woolly appearance, as if of a more tender and loofe texture. 
Something of the fame kind was obfervable in the ice of all 
the other folutions, diffidently didinguifhing it from any that 
can be formed of pure water. 
All the folutions of nitre were remarkably limpid, having 
no tendency to an opaque or turbid cad ; and accordingly they 
were very eafilv cooled below the freezing paint, and could not 
but with difficulty be made to (hoot till they had palled it many 
degrees. In two indances they cooled more than 10 degrees; 
namely, a folution of one part of nitre in 24 of water cooled 
{lowly to 19°!, and then {hooting, the thermometer came up 
to 30° ; and another folution, in which the nitre was to the 
water as 1 : 10, cooled rather below 16 0 , and having produced 
fome flellated crylfals, rofe, when the perfect congelation took 
place, up to 2 7 0 . 
As, when’ pure water is cooled below its freezing point, the 
lead particle of ice or fnow brought into contact with it caufes 
an in If ant congelation, I was curious to know whether the 
fame effedl would be produced when falts were diffolved in the 
water. Therefore, having one of thefe nitrous folutions, whole 
Vol. LXXVIII. Q.q proportions 
