Of WATER by HEAT. 



391 



inches deep, and 10 inches in diameter, with a circular hole in 

 the middle of the bottom, large enough to receive the top of the 

 jar. By means of a collar and cement I fecured this bafon, fo 

 that it encircled the upper part of the jar. 



The objedl of the contrivance was to have the means of ap- 

 plying a cooling medium to the fuperior portion of a cylinder 

 of water, and it anfwered the purpofe completely. I introduced 

 the ball of a thermometer through the tubulature, till the extre- 

 mity of it nearly reached the axis at three-fourths of an inch 

 above the riling of the bottom, and having fixed it in this fitua- 

 tion, I rendered the aperture water-tight, by a perforated cork 

 and lute. 



This very tall jar was placed on a table, with the interpofi- 

 tlon of fome folds of thick paper, in a room without a fire, of 

 the temperature 42°. 



I FILLED it with water of 50°, and poured into the bafon, 

 which embraced the top, a mixture of powdered ice and fait. 



From time to time I explored the temperature near the fur- 

 face, by inferting the bulb of a thermometer to the depth of 

 half an inch nearly in the axis. 



One o'clock, 

 In 1 1 minutes, 



— 15 



21 



— 31 



— 41 



— 5^ 



- I hour 6 min. 

 Vol. v.— p. II. 



Bottom. 



50° 

 46.+ 



45 



44— 

 42 



41 



40 

 39-5 



Top. 



48 

 46- 



44 



42 



Air. 

 42° 



4°-+ 34 



34 



3E 



'At this time a thin film of 

 I ice began to form in contadl 

 -with the glafs. 



In 



/ 



