34$ contraction of, watjjr by heat, 



■Tiiis ex penmen! is the counterpart of tlie foregoing, and fro;n 



theteftimony of the fame intfrurnents, it appears, that when a. 



cylinder of water of 53° is cooled by circumfluent iced fluid, 



the colder part of the water takes pofleflion of the bottom of the. 



veiTel, foas to eftablifli a difference of temperature from the fur- 



face, amounting fometimes to 8°-. And that as fop.n as the fluid 



at the bottom arrives at the 40th degree, the temperature of the 



. fluid in that fituation. is ifationary till the furface reaches the 



fame point. 



Whence the During the fubfequqnt refrigeration, the progrefs of the 



i^eductdasTn" 0001 "^ undergoes a total change. The thermometers tell 



the former ex- that the colder fluid rifes to the furface ; fo that the top gets 



peiimeut. the ftart of the bottom foon by 4°, and attains the lowed 



temperature of 34-° very long before the other talis to the fame 



degree. ■ 



Thefe circumftances, I think, lead to the conclufion, that by. 

 thelofs of caloric, water at .53° is contracted and rendered fp«» 

 cifically heavier, and that this continues to happen till the water 

 come to the temperature. of 40 9 , at which period an oppofite ef- 

 feci is produced ; for now the water, as it cools, becomes fpecifi- 

 cally lighter, or is expanded. 



In this, as well as the former experiment, the complete 

 change in the fituation, which the warmer and colder parts of 

 the fluid affected, in the progrefs both of the heating and cooU 

 ing, while every external circumftance of the procefs con- 

 tinued unaltered, is particularly worthy of temarL 

 Exp. 3. A tall Ex/>. Ill.Itookaglafsjar, 17.8 inches deep, and 4.5 in diameter 

 ^V^h'V 8 internal meafure, having a neck and tubulature very near the 

 containing water bottom. I provided alfo a cylindrical bafon of tinned iron A 

 at 50 , was _ 4, g j ncnes deep, and 10 inches in diameter, with a circular 

 upper fart by hole in the middle of the bottom, large enough to receive 

 ice and fait. the top of the jar. By means of a collar and cement I 

 ^refln^mckeft fecured this bafon, fo that it encircled the upper part of the 

 at bottom, till jar. 



c°nt* u*d fta*- T ne objefl of the contrivance was to have the means of ap* 

 tionary ; after plying a cooling medium to tlie fuperior portion of a cylinder 

 which the fur- Q f water< anc i jj anfwered the purpofe completely. I intrd- 

 freezing, and duced the ball of a thermometer through the tubulature, tilt 

 congealed, ^ e extremity of it nearly reached the axis at three-fourths oi 

 an inch above the riling of the bottom, and having fixed it in 

 this iiiuation/1 rendered the aperture water-tight, by a per* 



forated cork and lute. 



This 



