The Metal Monster by Abraham Merritt

For many minutes we stood silent, in the shadowy chamber, listening, each absorbed in his own thoughts. The thunderous drumming was continuous; sometimes it faded into a background for clattering storms as of thousands of machine guns, thousands of riveters at work at once upon a thousand metal frameworks; sometimes it was nearly submerged beneath splitting crashes as of meeting meteors of hollow steel.

But always the drumming persisted, rhythmic, thunderous. Through it all Ruth slept, undisturbed, cheek pillowed in one rounded arm, the two great pyramids erect behind her, watchful; a globe at her feet, a globe at her head, the third sphere poised between her and us, and, like the pyramids -- watchful.