for adjuftlng Thermometers. 819 
to its frame, a piece of woollen cloth being placed be- 
tween Gg and the cover, the better to prevent the efcape 
of the vapours. 
There were two pots of this kind ufed by us; one five 
inches in diameter and nine deep; the other, 4- in dia- 
meter and 23 deep. Two of the thermometers princi- 
pally ufed were the fhort ones, the brafs plate (ay) being 
placed only 3| inches above the top of the ball, and the 
boiling point riling not much above that plate : the third 
thermometer was much longer, the plate (g g) being 1 7 
inches above the ball. They were all three quick; the 
firft containing only i\ degrees to an inch ; the fecond 
5 0 ; and the third io°. The firft had a cylinder inftead 
of a ball i~ inch long and in diameter^; the two 
others had fpherical balls, about | of an inch in dia- 
meter. 
On trying thefe thermometers in the above mentioned 
veffels, with the water riling two or three inches above 
the top of the ball, we found fome variations in the 
height according to the different manner of making the 
experiment, but not very confiderable ; for the moll part 
there was very little difference whether the water boiled 
(c) Ifi the two fhort thermometers the quickfilver would have defcended into 
the ball when cold, had not the tube been fwelled a little, elofe to the ball, in 
-order to prevent it. 
5 K 2 
fait 
