VOL. LXXVI.] PHILOSOPHICAL TRANSACTIONS. Ill 



mometer, and taking out the thermometer, I choked the cylinder again in this 

 place. Introducing now the thermometer for the last time, I closed the opening 

 at the bottom of the globe at the lamp, taking care, before I brought it to the 

 fire, to turn the cylinder upside down, and to let the bulb of the thermometer 

 fall into the cylinder till it rested on the lower choak in the cylinder. By this 

 means the bulb of the thermometer was removed more than 3 inches from the 

 flame of the lamp. The opening at the bottom of the globe being now closed, 

 and the bulb of the thermometer being suffered to return into the globe, the 

 end of the cylinder was cut off to within about half an inch of the upper choak. 

 This being done, it is plain that the tube of the thermometer projected beyond 

 the end of the cylinder. Taking hold of the end of the tube, I placed the bulb 

 of the thermometer as nearly as possible in the centre of the globe, and observ- 

 ing and marking a point in the tube immediately above the upper choak of the 

 cylinder, I turned the cylinder upside down, and suffering the bulb of the ther- 

 mometer to enter the cylinder, and rest on the first or lower choak, the end of 

 the tube was cut off at the mark just mentioned, and a small solid ball of glass, 

 a little larger than the internal diameter or opening of the choak, was soldered 

 to the end of the tube, forming a little button or knob which, resting on the 

 upper choak of the cylinder, served to suspend the thermometer in such a manner 

 that the centre of its bulb coincided with the centre of the globe in which it was 

 shut up. The end o( the cylinder above the upper choak being now heated and 

 drawn out to a point, or rather being formed into the figure of the frustrum of a 

 hollow cone, the end of it was soldered to the end of a barometrical tube, by 

 the help of which the cavity of the cylinder and globe containing the thermo- 

 meter was completely voided of air with mercury ; when, the end of the cylin- 

 der being hermetically sealed, the barometrical tube was detached from it with a 

 file, and the thermometer was left completely shut up in a Torricellian vacuum, 

 the centre of the bulb of the thermometer being confined in the centre of the 

 glass globe, without touching it in any part, by means of the two choaks in the 

 cylinder, and the button on the end of the tube. 



I provided 2 of these instruments, as nearly as possible of the same dimen- 

 sions ; the one called N° 1 , being voided of air, in the manner above described ; 

 the other, N° 2, being filled with air, and hermetically sealed. With these two 

 instruments 1 made the following experiments on the 1 ith of July last, at Man- 

 heim, between the hours of 10 and 12, the weather being very fine and clear, 

 the mercury in the barometer standing at 27 inches 1 \ lines, Reaumur's ther- 

 mometer at 15°, and the quill hygrometer of the Academy of Manheim at 47°. 



Exper. 3, 4, 5, 6. — Putting both the instruments into melting ice, I let them 

 remain there till the mercury in the inclosed thermometers rested at the point 0°, 



