C 3°7 1 
II. New Experiments, upon Ice ; taken from 
Abbe Nolet, F. R. S< at Paris, and comma * 
nicated by J. T. Defaguliers, F.R.S. 
f 
l* TCE that begins to melt, and Water that begins 
JL to freeze, have always the fame Degree of 
Cold. 
2. That Cold may be increas’d by a Mixture of 
Salts. 
3. It has. been thought for a long time, that Salt- 
petre was moft fit to increafe the Cold of lee j but 
Experiments have {hewn, that few Salts increafe Cold! 
fo little as that Salt. Mix one Part of fine Saltpetre . : 
with two Parts of beaten Ice, and Monf. Reaumur’s. s 
Thermometer will defcend in it but 3 j- Degrees ber 
low the freezing Point. 
What had caus’d this Miftake, is, that People gene- 
rally made ufe of Salt-petre of the firft or fecond Melt- 
ing, as being the cheapeft 5 but that Saltpetre not be- 
ing purified, contains a great deal of Sea-Salt \ and it 
was in Proportion to the Quantity of the Sea-Salt that 
the Effeft was the greater. 
From thislaft Obfervation, one may deduce an ad- 
vantageous Method for trying Gunpowder 5 for as of 
the three Ingredients of which it is made up, Salt- 
petre is the only one that caii increafe the Cold of 
lee s if one Part of Gunpowder , or a little more, be 
mix’d with two Parts of Ice, and it increafes its Cold 
more than 3 §• Degrees, it is a Sign that the Saltpetre : 
contain’d in it is not well purified 5 and the beft Pow- 
der !' 
