Such in brief was the first of the contrivances which Mr. Edison invented for the approaching war with Mars. And these facts had become widely known. Additional experiments had completed the demonstration of the inventor's ability, with the aid of his wonderful instrument, to destroy any given object, or any part of an object, provided that that part differed in its atomic constitution, and consequently in its vibratory period, from the other parts. A most impressive public exhibition of the powers of the little disintegrator was given amid the ruins of New York. On lower Broadway a part of the walls of one of the gigantic buildings, which had been destroyed by the Martians, impended in such a manner that it threatened at any moment to fall upon the heads of the passers-by. The Fire Department did not dare touch it. To blow it up seemed a dangerous expedient, because already new buildings had been erected in its neighborhood, and their safety would be imperiled by the flying fragments. The fact happened to come to my knowledge. "Here is an opportunity," I said to Mr. Edison, "to try the powers of your machine on a large scale." "Capital!" he instantly replied. "I shall go at once." Disintegrating a Building. For the work now in hand it was necessary to employ a battery of disintegrators, since the field of destruction covered by each was comparatively limited. All of the impending portions of the wall must be destroyed at once and together, for otherwise the danger would rather be accentuated than annihilated. The disintegrators were placed upon the roof of a neighboring building, so adjusted that their fields of destruction overlapped one another upon the wall. Their indexes were all set to correspond with the vibration period of the peculiar kind of brick of which the wall consisted. Then the energy was turned on, and a shout of wonder arose from the multitudes which had assembled at a safe distance to witness the experiment. Only a Cloud Remained. The wall did not fall; it did not break asunder; no fragments shot this way and that and high in the air; there was no explosion; no shock or noise disturbed the still atmosphere--only a soft whirr, that seemed to pervade everything and to tingle in the nerves of the spectators; and--what had been was not! The wall was gone! But high above and all around the place where it had hung over the street with its threat of death there appeared, swiftly billowing outward in every direction, a faint, bluish cloud. It was the scattered atoms of the destroyed wall.