“Here we are, Harrison. Extract from stomach. Extract from vomit.
Extract from dish of fungus. Which is it you particularly want, Waters?”
“Doesn’t matter. Try the extract from the dish of fungus. It’ll be less
open to—that is, it is possibly better for our purpose. What’s this,
Lubbock?”
“That? Oh, that’s a fresh solution of muscarine I made myself for
control purposes, to assist in determining the strength.”
“Made from the fungus?”
“Yes. I don’t altogether guarantee that I’ve isolated the principle. But
it’s near enough.”
“Oh, yes. I’d like to have a look at that, too, if I may.”
“By all means.”
He brought the bottles out and set them on one of the laboratory tables.
In appearance they were indistinguishable—the same white salt that I
had seen before in the laboratory at St. Anthony’s.
Sir James Lubbock unlocked another cupboard, and produced a large, heavy
instrument, rather like a telescope fixed to a stand. He put it down
beside the two bottles and departed in search of water. While he was
preparing solutions from the respective bottles of muscarine, Waters
turned to me.
“You’d better have this quite clear in your mind—I mean, you’d like to
know what you may expect to see, exactly.”
“Yes,” I said. “At present I feel rather like the good lady in _The
Moonstone_, who wanted to know when the explosion would take place.”
“I’m afraid it won’t be so exciting as that. Cheer up, man, you look as
white as a sheet. At the further end of the instrument is a thin plate
of the semi-transparent mineral, tourmaline. You’ve seen it in
jewellers’ shops. Pretty stuff, and all that, and, what is more to the
purpose, it has a very finely foliated structure. In a ray of ordinary
light, the vibrations take place in all directions, but when passed
through a slice of tourmaline they are confined to one plane, and the
light is then polarised. We talked about that at dinner—you remember.
This slice of tourmaline is called the polariser. Right. Now at this
end, near the eyepiece, is a second slice of tourmaline, which can be
rotated, and which is called the analyser. Now, when the analyser is
turned so that its foliations are parallel to those of the polariser,
light will pass through both, but if the analyser is turned so that its
foliations are at right angles to those of the polariser, then no light
will pass and there will be darkness. All clear so far?”
“Perfectly.”
“Very well. Now, if, when the analyser is thus turned to darkness, I
place the solution of an optically active substance between the two
slices of tourmaline the light will—you can tell me that yourself—it’s
a _band_ of light, remember.”
“I remember. Yes. The band of light will be rotated as it passes
through.”
“That’s right. It will come round into line with the foliations of the
analyser, and——”
“Come through!” said I, triumphantly.
“Thank God for a man of intelligent mind. As you rightly say, it will
come through. And therefore you will see——”
“Light!” said I.
(Pom, pomty; pom, pomty—if I could have got rid of that relentless
drum-beat. My heart seemed to be going very heavily too.)
“But if,” went on Waters, with his eye on Sir James, who was stirring
his solutions with a glass rod over the sink, “if the substance should
be optically inactive—if, for example, it should turn out to be a
synthetic product, prepared from inorganic substances in the
laboratory—then it will not rotate the beam of polarised light. The
darkness will persist.”