390 



KNOBLAUCH OX RADIANT HEAT. 



Table XXIII. 



(The numbers marked with an * deserve notice on account of their difference, 



The above, and all subsequently mentioned reflecting surfaces, 

 were 8 centim. square in size. The numbers, which refer to a 

 direct deflection of 1 3°, in these, as in all other cases in which 

 it is not expressly otherwise stated, are each arithmetic means 

 of six observations ; those relating to a deflection of 25°, of 

 every four observations*. The former were obtained by means 

 of a multiplier, which M. Schellbach was good enough to lend 

 me ; the latter, by my own, which has been described at pp. 189, 

 190, the delicacy of which allowed me to produce greater deflec- 

 tions by the direct radiation of the reflected heat, without any 

 fear of disturbance from the absorption of heat by the reflecting 

 surface. 



I repeated each of the experiments six times merely because 

 they -were the first which I instituted with regard to this point ; 

 and thus I convinced myself, with perfect certainty, of the cor- 

 rectness of my results and of the limits of their accuracy. Sub- 

 sequently, when I experimented after greater practice, and in 

 summer under more favourable conditions of temperature, four 

 repetitions appeared to me more than sufficient. 



The relative superiority of the transmission by radiation of the 

 reflected heat in comparison with that unreflected, which was ob- 

 served in all (Table XXIII.) the instances detailed, completely 

 lays aside any doubt which might remain regarding the origin 



* Thus each of the former is the result of twelve separate readings from the 

 multiplier, since the direct deflection serving for comparison was controlled be- 

 fore each new insertion of a diathermanous body, and each of the latter is the 

 result of eight. 



