400 



On the CONTRACTION 



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

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

 reftion or another, excepting its adlual change of denfity. 



The thermometer evinces that the warm current fets dovpn- 

 wards, and carries the increafed temperature to the bottom. 

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

 grees, before the furface indicates the fmalleft acquifition of 

 heat. 



The Inference is plain, that the cold water is contra(fled by 

 the heat. 



The change of the eflPedl 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 alcending, 

 carried the increafe of temperature very rapidly to the furface, 

 fo that it foon furpaflTed 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 39t°> 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 commencement, 

 In 10 minutes, 



— 25 



— ss 



— an hour and 10 min. 

 __ 35 



— 2 hours, 



Bottom. 



39-5 



39+ 



39+ 



39 



39 



39— 



39— 



Top. Air. 



39-5 39' 



38+ 



2,^-5 *** At this time ice 

 began to be 

 formed on the 

 fide of the ve£- 

 fel. 



36- 

 3S 

 S4+ 

 34— 



This 



