[ I2S ] 
which were made nme hours after it was poured out of 
the tea kettle. The length of time which intervened 
between the firft appearance of ice upon the two waters 
was different in the different experiments. One caufe of 
this variety was plainly a variation of the temperature of 
the air, which became colder in the afternoon, and made 
the thermometer defcend gradually to 25°. Another 
caufe was the diflurbance of the water; when the un- 
boiled water was difturbed now and then by ftirring it 
gently with a quill tooth-pick, the ice was formed upon 
it as foon, or very nearly as foon, as upon the other ; and 
from what I faw, I have reafon to think, that were it to 
be flirred inceffantly, provided at the fame time the ex- 
periment were made with quantities of water, not muck 
larger or deeper than thefe, it would begin to-freeze full 
as foon. In one of thefe trials, having infpedted my tea 
cups when they had been an hour expofed, and finding 
ice upon the boiled water, and none upon the other, 1 
gently flirred the unboiled water with my tooth-pick, 
and faw immediately, under my eye, fine feathers of ice 
formed on its furface, which quickly encreafed in fizc 
and number, until there was as much ice in this cup as 
in the other, and all of it formed in one minute of time, 
or two at mofl. And in the reft of the trials, though the 
congelation began in general later in the unboiled water 
than in the other ; when it did begin in the former, the 
ice quickly encreafed fo as, in a very ftiort time, to equal, 
or nearly equal in quantity, that which had been formed 
more gradually in the boiled water. The opinion, 
S 2 therefore, 
