K. S. Magnet Steel.—The composition of this steel is given as C 0.4-0.8 per cent.; Co 30-40 per cent.; W 5-9 per cent.; Cr 1.5-3 per cent. Tempering is best effected by heating to 950°C. and quenching in heavy oil. Measurements of the residual magnetism for specimens of different composition gave values from 920 to 620 C.G.S. units; the coercive force for the same specimens ranged from 226 to 257 gauss. Artificial aging by heating in boiling water and by repeated mechanical shock reduced the residual magnetism by only 6 per cent. The hysteresis curves for a magnetizing force of ± 1,300 gauss were taken for annealed and tempered specimens; for the annealed specimen the coercive force was 30 gauss and for the hardened steel the coercive force 238 gauss and the energy loss per cycle 909,000 ergs. The hardness of annealed and tempered specimens was found to be 444 and 652 respectively on the Brinnell scale and 38 and 55 on the Shore scale. The microstructure of the hardened steel showed a finer grain than for the annealed.