$9* 



On the CONTRACTION 



Bottom. 



In i hour 44 min, 39.5 



In 47 hours, 





39-5 



— 5i hours, 



— 11 hours, u e. 



at midnight 



— 19 hours, u e. 

 next morning 



,} 

 } 



39 

 39 



39 



— 26 hours, 





40. 



— 32 





40 



— 41 





40 



_ 5 o 





41 



Top. 



{A cruft of ice of fome thick- 

 nefs now lined the glafs, 

 and air had fallen to 40 °. 



Cruft of ice complete. 



Air 40°. 



Air4o°. So much ice had 

 • melted that the cake was de- 

 1 tached from the fide of the vef- 

 fel, and floated. 

 Air 41 °. Ice not all melted. 

 Air 42 °. Ice not entirely gone. 



This long protracted experiment prefents fome ftriking fads, 

 and its general import, with regard to the fubject of inveftiga- 

 tion, agrees with the preceding. In it we fee, that when the 

 frigorific mixture abftracted caloric from the upper extremity of 

 a cylinder of water, nearly 18 inches long, and at 50°, the re- 

 duction of temperature appeared fooner, and advanced quicker, 

 at its lower extremity than in the axis at the top, not two and a 

 half inches diftant from the cooling power. No one can entertain 

 a doubt that this is owing to a current of cooled and condenfed 

 fluid defcending, and a correfponding one of a warmer tempera- 

 ture afcending. Now, if water obferved the fame law that other 

 bodies do, and had no peculiarity of conftitution, the fame pro- 

 grefs of cooling fhould continue. This, however, the experi- 

 ment teaches us, is not the cafe : as foon as the fluid at the bot- 

 tom exhibits a temperature of 40 °, it ceafes. The colder fluid 

 remains at top, and quickly lofing temperature, ere long begins 

 to freeze- The continuance of the colder fluid at the furface 

 furely denotes, that it is not more denfe than the fubjacent 



warmer 



