CONTRIBUTIONS TO MOLECULAR PHYSICS. 301 
spiral is brought near its point of fusion. Kemarkable 
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 wrth chloroform. For 
the cube at 100 degrees C., coated with kimpblack, 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-flame the absorption by chloro- 
form is also considerably in excess of that by bisulphide 
of carbon; while, for the flame of a Bunsen'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 flaine the. 
