400 



On the CONTRACTION 



tion has an equal {hare of the column of cold fluid above it and 

 beneath it. There is nothing to determine its courfe in one di- 

 rection or another, excepting its actual change of denfity. 



The thermometer evinces that the warm current fets down- 

 wards, and carries the increafed temperature to the bottom. 

 There, this inflrument indicates the fuccefuve rife of feveral de- 

 grees, before the furface indicates the fmalleft acquifition of 

 heat. 



The inference is plain, that the cold water is contracted by 

 the heat. 



The change of the effecl: of heat is equally well illuftrated by 

 this experiment. 



No fooner did the inferior portion attain the temperature of 

 39 , than the heated fluid altered its courfe, and, by afcending, 

 carried the increafe of temperature very rapidly to the furface, 

 fo that it fbon furpafTed the bottom, and continued to rife, while 

 the other remained flationary. 



Experiment VI. 



I filled the jar ufed in the laft experiment with water of 

 temperature 39^° > the air and the fupport being at 39 °. Difpo- 

 fing the thermometers in the ufual manner, I introduced a mix- 

 ture of fnow and fait into the bafon. 



At commencem 

 In 10 minutes, 



ent, 



10 min. 

 35 



Bottom. 



39-5 



39+ 



39+ 



39 



39 



39— 



39— 



39— 



Top. 



39-5 



38+ 



3&5 *** 



36- 



35 



34+ 



34— 



33+ 



Air. 



39° 



At this time ice 

 began to be 

 formed on the 

 fide of the vef- 

 fel. 



— 25 



"—35 



— 55 



— an hour and 



— 2 hours, 



This 



