Friday, March 25, 2016

Single-Jack

"It had been used by some miner in the old days when rock-drills were driven home in a low tunnel with a man swinging a hammer in one hand; four pounds was about the weight a man could handle in that way, and it was called a single-jack because it was managed one-handedly."

Excerpt From: George R. Stewart. "Earth Abides." Houghton Mifflin Harcourt (www.hmhco.com). iBooks.
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