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preventing it to become, in the leaft, colder than the 
freezing point, without beginning to freeze, in confe- 
quence of which its congelation mull begin immediately 
after it is cooled to that point. When I refiecSl upon 
this idea, I remember a fa6l which appears to me to fup- 
port it ftrongly. Fahrenheit was the firft perlbn who 
difcovered that water, when prefei'ved in tranquillity, 
may be cooled fome degrees below the freezing point 
without freezing. He made the difcovery While he was 
endeavouring to obtain ice from water that had been 
purged of its air : with this intention he had put fome 
water into little glafs globes, and having purged it of air, 
by boiling and the air-pump, he fuddenly fealed up the 
globes, and then expofed them to the frofty air. He was 
furprizedto find the water remain unfrozen much longer 
than he cxpe6ted, when at laft he opened fome of his 
globes, in order to apply a thermometer to the water, or 
otherwife examine what Ifate it was in. The immediate 
confequence of the admilTion of the air w'as a hidden 
congelation which happened in the \vater; and in the 
lefi c>f his globes, a fimilar produdlion of ice was occa- 
fioned % lhaking them. The inference that may be 
drawn from thefe experiments of Fahrenheit’s is fuffi- 
ciently obvious; it appears to me to remove all doubt 
with regard to the above luppofition. Before thefe 
experiments of Fahrenheit occurred to my memory, I 
had planned a few, fuggefied by the above fuppofition, 
that might have led to the fame conclufion ; but the fliort 
duration of the froft, for one day only, did not give me 
time to put them in execution. 
XIV. EX PE- 
