in various Substances. 407 



ball (which was now uppermost) left the space surround- 

 ing the bulb of the thermometer free of air. The mer- 

 cury having totally quitted the glass ball, and having 

 sunk in the tube to the height of 28 inches (being the 

 height of the mercury in the common barometer at that 

 time), with a lamp and a blow-pipe I melted the tube to- 

 gether, or sealed it hermetically, about three quarters of 

 an inch below the ball, and, cutting it at this place with 

 a fine file, I separated the ball from the long barometri- 

 cal tube. ' The thermometer being afterwards filled with 

 mercury in the common way, I now possessed a ther- 

 mometer whose bulb was confined in the center of a 

 Torricellian vacuum > and which served at the same time 

 as the body to be heated, and as the instrument for 

 measuring the Heat communicated. 



Experiment No. i. 



With this instrument (see Fig. i) I made the fol- 

 lowing experiment. Having plunged it into a vessel 

 filled with water, warm to the i8th degree of Reaumur's 

 scale, and suffered it to remain there till it had acquired 

 the temperature of the water, that is to say, till the 

 mercury in the inclosed thermometer stood at 18, I 

 took it out of this vessel and plunged it suddenly into 

 a vessel of boiling water, and holding it in the water 

 (which was kept constantly boiling) by the end of the 

 tube, in such a manner that the glass ball, in the center 

 of which was the bulb of the thermometer, was just 

 submerged, I observed the number of degrees to which 

 the mercury in the thermometer had arisen at different 

 periods of time, counted from the moment of its im- 

 mersion. Thus, after it had remained in the boiling 

 water i min. 30 sec. I found the mercury had risen from 



