the lesson is not without its value. That spot of grease is free nitro-
glycerine that has oozed out from the dynamite. Therein rests, perhaps,
the only danger in handling dynamite. As I have shown you, you can
smash up dynamite on an anvil without danger, but if a hammer happened
to strike a spot of free nitroglycerine it would explode in a moment. I
beg to apologize to you for my momentary neglect."

A man rose up in the middle of the hall, and it was some little time
before he could command voice enough to speak, for he was shaking as if
from palsy. At last he said, after he had moistened his lips several
times:--

"Professor, we are quite willing to take your word about the explosive.
I think I speak for all my comrades here. We have no doubt at all about
your learning, and would much prefer to hear from your own lips what
you have to say on the subject, and not have you waste any more
valuable time with experiments. I have not consulted with my comrades
before speaking, but I think I voice the sense of the meeting." Cries
of "You do, you do," came from all parts of the hall. The Professor
once more beamed upon them benevolently.

"Your confidence in me is indeed touching," he said, "but a chemical
lecture without experiments is like a body without a soul. Experiment
is the soul of research. In chemistry we must take nothing for granted.
I have shown you how many popular errors have arisen regarding the
substance with which we are dealing. It would have been impossible for
these errors to have arisen if every man had experimented for himself;
and although I thank you for the mark of confidence you have bestowed
upon me, I cannot bring myself to deprive you of the pleasure which my
experiments will afford you. There is another very common error to the