Now Mr. Edison had been able to ascertain the vibratory swing of many well known substances, and to produce, by means of the instrument which he had contrived, pulsations in the ether which were completely under his control, and which could be made long or short, quick or slow, at his will. He could run through the whole gamut from the slow vibrations of sound in air up to the four hundred and twenty-five millions of millions of vibrations per second of the ultra red rays. Having obtained an instrument of such power, it only remained to concentrate its energy upon a given object in order that the atoms composing that object should be set into violent undulation, sufficient to burst it asunder and to scatter its molecules broadcast. This the inventor effected by the simplest means in the world--simply a parabolic reflector by which the destructive waves could be sent like a beam of light, but invisible, in any direction and focused upon any desired point. I had the good fortune to be present when this powerful engine of destruction was submitted to its first test. We had gone upon the roof of Mr. Edison's laboratory and the inventor held the little instrument, with its attached mirror, in his hand. We looked about for some object on which to try its powers. On a bare limb of a tree not far away, for it was late in fall, sat a disconsolate crow. "Good," said Mr. Edison, "that will do." He touched a button at the side of the instrument and a soft, whirring noise was heard. "Feathers," said Mr. Edison, "have a vibration period of three hundred and eighty-six million per second." He adjusted the index as he spoke. Then, through a sighting tube, he aimed at the bird. "Now watch," he said. Another soft whirr in the instrument, a momentary flash of light close around it, and, behold, the crow had turned from black to white! "Its feathers are gone," said the inventor; "they have been dissipated into their constituent atoms. Now, we will finish the crow." Instantly there was another adjustment of the index, another outshooting of vibratory force, a rapid up and down motion of the index to include a certain range of vibrations, and the crow itself was gone--vanished in empty space! There was the bare twig on which a moment before it had stood. Behind, in the sky, was the white cloud against which its black form had been sharply outlined, but there was no more crow. "That looks bad for the Martians, doesn't it?" said the Wizard. "I have ascertained the vibration rate of all the materials of which their war engines, whose remains we have collected together, are composed. They can be shattered into nothingness in the fraction of a second. Even if the vibration period were not known, it could quickly be hit upon by simply running through the gamut." "Hurrah!" cried one of the onlookers. "We have met the Martians and they are ours." Such in brief was the first of the contrivances which Mr. Edison invented for the approaching war with Mars.