CONTRIBUTIONS TO MOLECULAR PHYSICS. 301 



spiral is brought near its point of fusion. Remarkable 

 cases of inversion as to transparency also occur. For barely 

 visible redness formic ether is more opaque than sulphuric; 

 for a bright red heat both are equally transparent; while, 

 for a white heat, and still more for a higher temperature, 

 sulphuric ether is more opaque than formic. This 

 result gives us a clear view of the relationship of the 

 two substances to the luminiferous ether. As we intro- 

 duce waves of shorter period the sulphuric ether aug- 

 ments most rapidly in opacity; that is to say, its accord 

 with the shorter waves is greater than that of the formic. 

 Hence we may infer that the atoms of formic ether 

 oscillate, on the whole, more slowly than those of sulphuric 

 ether. 



When the source of heat is a Leslie's cube coated with 

 lampblack and filled with boiling water, the opacity of 

 formic ether in comparison with sulphuric is very decided. 

 With this source also the positions of chloroform and iodide 

 of methyl are inverted. For a white-hot spiral, the absorp- 

 tion of chloroform vapor being 10 per cent., that of iodide 

 of methyl is 16; with the blackened cube as source, the 

 absorption by chloroform is 22 per cent., while that by the 

 iodide of methyl is only 19. This inversion is not the 

 result of temperature merely; for when a platinum wire, 

 heated to the temperature of boiling water, is employed as 

 a source, the iodide continues to be the most powerful 

 absorber. All the experiments hitherto made go to prove 

 that from heated lampblack an emission takes place which 

 synchronizes in an especial manner with chloroform. For 

 the cube at 100 degrees C., coated with lampblack, the 

 absorption by chloroform is more than three times that by 

 bisulphide of carbon; for the radiation from the most 

 luminous portion of a gas-flume the absorption by chloro- 

 form is also considerably in excess of that by bisulphide 

 of carbon; while, for the flame of a Bunseu's burner, from 

 which the incandescent carbon particles are removed by 

 the free admixture of air, the absorption by bisulphide of 

 carbon is nearly twice that by chloroform. The removal 

 of the carbon particles more than doubles the relative trans- 

 parency of the chloroform. Testing, moreover, the radi- 

 ation from various parts of the same flame, it was found 

 that for the blue base of the flame the bisulphide of carbon 

 was most opaque, while for all other parts of the flame the 



