Combinations in Chubb lock, 436; Yale lock, _436_, _437_. Yellow spot, in eye, 251; yellow, in eye, 251; yellow, in eye, 251. Spring balance 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 induction coil, 122. Pump, air, 340; bucket, 352, _353_; force, 354; most marvellous, 355; Westinghouse air, 199. Railway brakes, 187; signalling, 200. Rays, converging and diverging, _256_; heat, concentrated by lens, _232_; light, 232, 235, 236, 237.