Flight Through Tomorrow by Stanton A. Coblentz

There came a whirring in my head, and another blank interval; and when I regained my senses I knew that another period of time had passed, possibly months or even years. I stood on the palisade above the river, near the entrance of the caves; and the sun was bright above me; but there was no brightness in the men and women that trailed out of a small circular hole in the ground. Drab as dock-rats, and pasty pale of countenance as hospital inmates, and with bent backs and dirty, tattered clothes and a mouse-like nosing manner, they emerged with the wariness of hunted refugees; and they flung up their hands with low cries to shield them from the brilliance of the sun, to which they were evidently unaccustomed. From the packs on their backs and the bundles in their hands, I knew that they were emerging from their subterranean refuge, to try to begin a new life in the ravaged world above; and my heart went out to them, for I saw that, few as they were -- not more than fifty in all -- they were the sole survivors of a once-populous region, and would have a bitter fight to wage in the man-made wilderness that had been a world metropolis.

But as they roamed above through the waste of ash and rubble, and as they wandered abroad where the fields had been and saw how every brush and tree had been seared from the earth or poisoned by chemical brews, I knew that their fight was not merely a bitter one -- it was hopeless. And I heard them muttering among themselves, "We have not even any tools!", and again, "We have no fuel left for the great machines!". For they had lived in a highly mechanical world, and the technicians who alone understood the workings of that world had all been destroyed, and the sources of power had all been cut off -- and power was the food without which they could not long survive.