Signalling, and vacuum tubes, 231 by light and sound waves, 47 in the war, 221 ff. Smoke, production and use of, 169 Soda lime, in gas warfare, 158 Specialization, in research, 405 ff. Tank, leak-proof, for airplanes, 47 Telegraph lines abroad, 225 Telephone lines abroad, 225 Trade tests, cost of, 382 Trowbridge, A., 63 ff. Vacuum tubes, and signalling, 231 War neuroses, 291 Water, purification of, 281 West, C. J., 148 ff. Wilson, Woodrow, letter, 15 surgical treatment of, 312 ff. Yerkes, R. M., 351 ff, |