guish at an early period the exact difference between true movement and mere undulation; and we must remember that although the waves of light are propagated at the rate of 185,000 miles a second, still there is no transmission of any material substance at this marvellous rate. The same observation applies to sonorous vibrations transmitted through the air.
Thus we are constrained to admit peaceably the truth of the undulatory hypothesis as compared with the corpuscular theory. I say peaceably, because I am forcibly reminded by the contrast I have made between the two theories of an anecdote related of one of the greatest monsters who ever walked this earth, but who was afterwards struck down in the midst of his power by the hand of a weak girl. I allude to the infamous Marat, who one day presented himself at the house of Dr. Charles, a celebrated natural philosopher, of the time of the first French Republic, in order to advance certain notions of his own against the optical principles that Newton has left behind in his Principia, and other works—also, to oppose certain theories connected with electrical science. Dr. Charles, who did not approve of Marat's wild notions, undertook to convince him of his errors. But instead of discussing the matter peaceably, Marat allowed himself to be carried away by his temper, which was naturally very violent. Every argument advanced by his antagonist seemed to increase his rage, until at last he lost all control over himself, drew his small sword, and rushed upon his opponent. The doctor, who was unarmed, had to exercise all his powers to prevent himself from being wounded, and being much more stoutly built than Marat, he at last succeeded in throwing him down, and wresting his sword from him, which he immediately took care to break. Whether it was the violence of the fall, the shame he felt at being doubly beaten, or the effects of his fit of passion, does not
