Emission and Transmission of Heat 



61 



bent at i, serving as a drain for the water of condensation and any 

 excess of steam. Three quarters of an inch below the cylinder a 

 bed, the tube h i was provided with three projecting pieces of iron 



Fig. 171 



three quarters of an inch wide, serving to sustain the wooden disc 

 / m, which was put in place by removing the horizontal tube i k 

 and passing the iron projections through corresponding openings 

 in the disc; by a slight twist the disc was then held in position. Be- 

 fore introducing the disc there had been fixed upon its upper side 

 a cylinder n p q r of very thin glass, open at both ends, and of the 

 same diameter as the disc, and maintained in position by means of 

 a band of paper glued to both the glass and wood. The whole 

 surface of the glass cylinder was covered with paper and the sheet 

 of paper projected at both ends for nearly four inches. The mater- 

 ial to be experimented on was placed between the two cylinders 

 abed and n p q r, and the paper cylinders forming prolongations 

 of the glass cylinder were filled with carded cotton. The appa- 

 ratus which we have just described was suspended within the con- 

 stant temperature chamber, used in the experiments on cooling, by 

 means of the supports s t. Steam was allowed to flow into the tin 

 cylinder a b cd, often for several hours, so as to be well assured that 

 a constant regime had been established. 



847. The temperature of the outer surface of the cylinder 



