The Professor looked with kindly sympathy over his audience as he allowed the yellow mixture to percolate slowly through his fingers back into the box again. Ever and anon he took up a fresh handful and repeated the action. The Anarchists in the audience exchanged uneasy glances one with the other. "Yet," continued the Professor, "it will be useful for us to consider this substance for a few moments, if but for the purpose of comparison. Here," he said, diving his hand into another box and bringing up before their gaze a yellow brick, "is dynamite in a compressed form. There is enough here to wreck all this part of London, were it exploded. This simple brick would lay St. Paul's Cathedral in ruins, so, however antiquated dynamite may become, we must always look upon it with respect, just as we look upon reformers of centuries ago who perished for their opinions, even though their opinions were far behind what ours are now. I shall take the liberty of performing some experiments with this block of dynamite." Saying which the Professor, with his free arm, flung the block of dynamite far down the aisle, where it fell on the floor with a sickening thud. The audience sprang from their seats and tumbled back one over the other. A wild shriek went up into the air, but the Professor gazed placidly on the troubled mob below him with a superior smile on his face. "I beg you to seat yourselves," he said, "and for reasons which I have already explained, I trust that you will not applaud any of my remarks. You have just now portrayed one of the popular superstitions about dynamite, and you show by your actions how necessary a lecture of this sort is in order that you may comprehend thoroughly the substance with which you have to deal. That brick is perfectly harmless, because it is frozen. Dynamite in its frozen state will not explode--a fact well understood by miners and all those who have to work with it, and who, as a rule, generally prefer to blow themselves to pieces trying to thaw the substance before a fire. Will you kindly bring that brick back to me, before it thaws out in the heated atmosphere of this room?" One of the men stepped gingerly forward and picked up the brick, holding it far from his body, as he tip-toed up to the platform, where he laid it down carefully on the desk before the Professor. "Thank you," said the Professor, blandly. The man drew a long breath of relief as he went back to his seat.