RADIANT HEAT AND ITS RELATIONS 93 



iheir place of convergence. With a proper thermometer 

 it could be proved that even the air at the focus is just as 

 cold as the surrounding air. And mark the conclusion to 

 which this leads. It proves the ether at the focus to be 

 practically detached from the air — that the most violent 

 ethereal motion may there exist, without the least aerial 

 motion. But, though you see it not, there is sufficient heat 

 at that focus to set London on fire. The heat there is 

 competent to raise iron to a temperature at which it throws 

 off brilliant scintillations. It can heat platinum to white- 

 ness, and almost fuse that refractory metal. It actually 

 can fuse gold, silver, copper, and aluminium. The mo- 

 ment, moreover, that wood is placed at the focus it bursts 

 into a blaze. 



It has been already affirmed that, whether as regards 

 radiation or absorption, the elementary atoms possess but 

 little power. This might be illustrated by a long array of 

 facts; and one of the most singular of these is furnished 

 by the deportment of that extremely combustible sub- 

 stance, phosphorus, when placed at the dark focus. It 

 is impossible to ignite there a fragment of amorphous 

 phosphor as. But ordinary phosphorus is a far quicker 

 combustible, and its deportment toward radiant heat is 

 still more impressive. It may be exposed to the intense 

 radiation of an ordinary fire without bursting into flame. 

 It may also be exposed for twenty or thirty seconds at 

 an obscure focus, of sufficient power to raise platinum to 

 a red heat, without ignition. Notwithstanding the energy 

 of the ethereal waves here concentrated, notwithstanding 

 the extremely inflammable character of the elementary 

 body exposed to their action, the atoms of that body 

 refuse to partake of the motion of the powerful waves 



