George O. Smith 
One of Three 

Excerpt: "The bit of whitish substance fluoresced, which of course was quite natural. It also vibrated very faintly, which was unnatural. At least, this property had not been known previously-which is really saying little since the material had been compounded from artificial radioisotopes from the big piles. All too little was known about such items and the fact that this one was vibrating ever so faintly whenever the electron beam struck it was interesting both from a scientific and a lay curiosity standpoint. Ed Bronson blinked a bit and decided that he had made some mistake. It had ceased to vibrate. Ed cracked the experimental tube and removed the irregular lump. It had been hoped to produce a more brilliant and higher-contrast phosphor for television screens. But if it was going to vibrate…"