Emission and Transmission of Heat 



33 



placed midway between those of the two adjacent rows. Similar 

 strips are placed in the opening A*"and P. QR and Q R' are two 

 sealed half cylinders of tin full of water at the oridinary tempera- 

 ture, they serve to close, to the desired extent, the opening AF 

 of the chamber. ST is an adjustable tripod bearing three glass 

 tubes terminated by wooden stoppers, into which penetrate cop- 

 per stems soldered to the vessel of which the rate of cooling is to 

 be determined. 



Fig. 149 



783. Figures 151 and 152 show a vertical and horizontal 

 section of a spherical vessel and its agitator. 



The plates, which agitate the water are carried by six pieces 

 of iron wire in the shape of a semi -circle. These are attached 

 below to the axial stem and above to a small horizontal ring which 

 allows of the insertion of the thermometer through the tubular 

 orifice shown. The cylindrical vessels of large diameter are ar-. 

 ranged in the same way (fig. 153 and 154). 



When the cylinders are of small diameter the agitator is 

 placed on one side (fig. 155 and 156). 



784. I show in figures 157 to 161 the different methods of 



