414 



KNOBLAUCH ON RADIANT HEAT. 



Although the tables given at p. 403-409, which exhibit the 

 variations in the heat reflected when different sources of heat 

 are used, are arithmetical means of four repetitions of the 

 experiments, the latter (p. 410-413) are derived from two series 

 of observations only, which appeared to be sufficient, because 

 the object was merely to make an accurate comparison of 

 each pair of surfaces ; and, moreover, there is less cause for 

 mistrust in cases of similarity than where differences are con- 

 cerned. 



In the following table, those bodies which diffusely reflect the 

 rays of heat in such a manner that when transmitted through 

 red glass, blue glass, alum, rock salt, calcareous spar and gyp- 

 sum, they are undistinguishable from one another, are arranged 

 in vertical series. In those under 1. only are no differences per- 

 ceptible after reflexion in this manner on comparison with the 

 unreflected heat: — 



Table XLIII. 



10. 



Yellow leather. 

 Brown Spanish 

 leather. 



Light cloth. 

 Blai k cloth. 



Blue woollen 



tapestry. 

 Green woollen 



tapestry. 



White wool. 

 Red wool. 



Cinnabar. 

 Peroxide of 

 copper. 



Those of the following substances, which are arranged in one 

 and the same column, exhibit very similar, although not identical 

 deportment in this respect : — 



