64 FRAGMENTS OP SCIENCE. 
these invisible rays are brought to a focus, at a distance of 
several feet from the electric lamp, the dark rays form an 
invisible image of their source. By proper means, this 
image may be transformed into a visible one of dazzling 
brightness. It might, moreover, be shown, if time per- 
mitted, how, out of those perfectly dark rays, could be ex- 
tracted, by a process of transmutation, all the colors of the 
solar spectrum. It might also be proved that those rays, 
powerful as they are, and sufficient to fuse many metals, 
can be permitted to enter the eye, and to break upon the 
retina, without producing the least luminous impression. 
The dark rays being thus collected, you see nothing at 
their 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 
whiteness, and almost fuse that refractory metal. It 
actually can fuse gold, silver, copper, and aluminium. The 
moment, 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 substance, 
phosphorus, when placed at the dark focus. It is 
impossible to ignite there a fragment of amorphous phos- 
phorus. 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 radia- 
tion 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 
