Stick your head out, old man, and see where it went to."

Out I started to thrust my head, but a sharp blow on the forehead
caused me to recoil. I rubbed my bruised brow and gazed with reproachful
inquiry at Paul, who was laughing in gleeful, boyish fashion.

"Well?" he said.

"Well?" I echoed.

"Why don't you investigate?" he demanded. And investigate I did. Before
thrusting out my head, my senses, automatically active, had told
me there was nothing there, that nothing intervened between me and
out-of-doors, that the aperture of the window opening was utterly empty.
I stretched forth my hand and felt a hard object, smooth and cool and
flat, which my touch, out of its experience, told me to be glass. I
looked again, but could see positively nothing.

"White quartzose sand," Paul rattled off, "sodic carbonate, slaked lime,
cutlet, manganese peroxide--there you have it, the finest French plate
glass, made by the great St. Gobain Company, who made the finest plate
glass in the world, and this is the finest piece they ever made. It cost
a king's ransom. But look at it! You can't see it. You don't know it's
there till you run your head against it.

"Eh, old boy! That's merely an object-lesson--certain elements, in
themselves opaque, yet so compounded as to give a resultant body which
is transparent. But that is a matter of inorganic chemistry, you say.
Very true. But I dare to assert, standing here on my two feet, that in
the organic I can duplicate whatever occurs in the inorganic.

"Here!" He held a test-tube between me and the light, and I noted the
cloudy or muddy liquid it contained. He emptied the contents of another
test-tube into it, and almost instantly it became clear and sparkling.

"Or here!" With quick, nervous movements among his array of test-tubes,
he turned a white solution to a wine color, and a light yellow solution
to a dark brown. He dropped a piece of litmus paper into an acid, when
it changed instantly to red, and on floating it in an alkali it turned
as quickly to blue.

"The litmus paper is still the litmus paper," he enunciated in the
formal manner of the lecturer. "I have not changed it into something
else. Then what did I do? I merely changed the arrangement of its
molecules. Where, at first, it absorbed all colors from the light but
red, its molecular structure was so changed that it absorbed red and all
colors except blue. And so it goes, ad infinitum. Now, what I purpose
to do is thi