JOHNSON J. HOOPER, the author of a double purpose. [Illustration: FIG. 117_b_.] [Illustration: FIG. 209.--The winding mechanism for watches, 425. Rods of Corti, 274. Ruhmkorff coil, 121, _122_. Safety-valve, 32, _33_, 391. Sand-glasses, 411. Scissors, action of, _450_. Secondary winding of.