( 811 ) 



The antimonito plate had a thickness of aboul 1 in. in. and a 

 section which niav have amounted to about '/, c.m s . 



Now if a source of light was placed at I, the remaining deflection 

 of' about l,8c.m. obtained at a 10,5 Volts' tension was only increased 

 by 2 m.m., i. e. by about 11 %• M» however, the light was placed 

 at the same distance in II, the increase amounted to about 1 J, 5 m.m., 

 i.e. 64%. 



K t 



K-, 



■2*- /. / 



L II 



In the former case the plate A is viz. in the shadow of K if and 

 so receives but very little light reflected by the walls; in the latter 

 case, however, the radiation is direct. 



§ 5. If a thick plate of colourless plate-glass is placed between 

 the source of light in II and the apparatus, the remarkable fact 

 presents itself that the deflection is considerably increased. The 

 explanation of this phenomenon was obvious. For a copper bar, 

 heated to some hundreds of degrees, and brought near the apparatus, 

 immediately diminished the obtained deflection greatly. Hence - 

 and this is a most remarkable result — rise of temperature has an 

 influence directly opposed to that of radiation of light : ii enlarges 

 the resistance instead of diminishing it, as rays of light do. 



