34 



Emission and Transmission of Heat 



supporting the vertical and horizontal cylinders in a frame placed 

 within the chamber. The object of these arrangements is to ren- 

 der the cylinders perfectly motionless in spite of the movements 

 of the agitator. The frames are of iron or brass, the stems a, a, a, 



LJ 



Fig. 152. 



Fig 153 and 154. 



Figs. 155 and 156 



are very thin and of fir wood ; they project into very small me- 

 tallic appendices soldered to the vessels. When the cylinders are 

 placed horizontally, the stem of the agitator turns in a cork which 

 closes the tubular opening. There is a little play between the 

 stem and cork, but the water does not escape on account of the 

 expansion of the small quantity of air remaining in the vessel. 

 This expansion is due to the contraction of the water by cooling. 



Figure 162 is a section of a cylindrical vessel, with hemi- 

 spherical ends, provided with two agitators. 



When the vessels are long and of small diameter, cylinders 



