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It is well known, that the greateft Degree of Heat 
in common Water is that which it acquires by boil- 
ing; that is to fay, if Water is put upon the Fire, it 
grows by degrees hotter and hotter, till it quite boils; 
but, after that, though there be never fo much Fire 
added, and it (land never fo long upon it, it will never 
grow hotter than it was on the firft Inftant, when it 
began to boil. Hence the Degree of Heat of boiling 
Water is looked upon as fixed and invariable. 
Fahrenheit , that ingenious Matter in Mechanics, 
fo well known by his Mercurial Thermometers, is 
the firft who has remarked the contrary. He obferved, 
that the Heat of boiling Water was greater when the 
Air was heavy (that is to fay, when the Mercury 
flood higher in the Barometer) ; and, on the contrary, 
the Heat was lefs when the Air was lighter. 
Mr. Le Mormier the younger, who has obliged us 
with a Tranflation of Mr. Cote's Le&ures in Natural 
Philofophy, with excellent Notes upon thefaid Work, 
has put Fahrenheit’s Difcovery paft all Doubt, and 
has very much improved it. 
On the 6th of QCtoher i739> being provided with 
a Barometer, and a Mercurial Thermometer of M. 
CDelifle, he climbed up to the higheft Top of the 
Canigou, a Mountain in RonJJUlon , which pafles for 
the higheft among the Fyrenees: There he found 
his Barometer to ftand at 20 Inches 2 ~ Lines ; whilft 
at Ferpignan it flood at 28 Inches 2 Lines. The 
Difference between the Heat of the Water which he 
boiled there, and that which he boiled at Ferpignan> 
was 15 Degrees of his Thermometer. 
The 
