HEAT OR CALORIC. 



75 



CIRCULATION INDISPENSABLE, TO AN EFFECTUAL COMMUNICATION 

 OF HEAT IN LIQUIDS. 



6. Different effects of heat on the upper or lower strata of a liquid. 



H 



B 



"A glass jar, about 30 inches in 

 height, is supplied with as much 

 water as will rise in it within a few 

 inches of the brim. By means of 

 a tube* descending to the bottom, 

 a small quantity of blue coloring 

 matter is introduced below the col- 

 orless water, so as to form a stratum 

 as represented at A, in the engrav- 

 ing. A stratum, differently colored, 

 is formed in the upper part of the 

 vessel, as represented at B. A tin 

 cap, supporting a hollow tin cylin- 

 der, closed at bottom, and about an 

 inch less in diameter than the jar, 

 is next placed as it is seen in the 

 drawing, so that the cylinder may 

 be concentric with the jar, and de- 

 scend about 3 or 4 inches into the 

 water." 



" The apparatus being thus pre- 

 pared, if an iron heater, H, while 

 red hot, be placed within the tin 

 cylinder, the colored water, about 

 it, soon boils ; but the heat pene- 

 trates only a very small distance be- 

 low the tin cylinder, so that the col- 

 orless water, and the colored stra- 

 tum, at the bottom of the vessel, 

 remain undisturbed, and do not 

 But if the ring, R, be placed, while red hot, upon the iron 



mingle. 



R 



stand which surrounds the jar at S S, the portion of the liquid, color- 

 ed blue, being opposite to the ring, will rise until it encounters the 

 warmer, and of course lighter particles, which have been in contact 

 with the tin cylinder. Here its progress upwards is arrested ; and in 



* e. g. A dropping tube. 



