A simple experiment has disastrous results for the planet Earth!

Excerpt

Atwar spun his motor-chair deftly about and rolled over to the blue enameled all-metal cabinet. Pulling out a drawer he withdrew a small instrument and sped back to his slate-topped workbench. Once there he made a few adjustments in the weird machine that stood upon it.

A weird machine it was, a jumbled mass of wires that led to a small, porcelain-like chamber within which the wires seemed to be fused into a solid mass. Above the chamber was a compound microscope of peculiar shape, with a double eyepiece and a sort of keyboard mounted on its side. There were other peculiar things about the microscope; for instance had one been able to examine it, he would have noticed that all the illumination was provided through a microscopic aperture underneath the chamber, and that the light was artificial, provided by a mercury lamp of some type and filtered through two lenses before it reached the hole. Had Atwar been in a talkative mood, which he never was, he would have explained, that the purpose of those lenses was to increase the magnifying power in a peculiar system of his own.