1. Alloys were prepared containing 14, 16, 18, 30, 38, and 48 per cent, of tin, and the remainder copper and manganese in the ratio 7 : 3.
2. Tests were carried out at different temperatures on the materials as cast, normalised, annealed, and quenched.
3. At 15° C in the normalised condition the six alloys gave I respectively equal to 55, 77, 82, 0·4, 96, and 1, for H = 100.
4. When cooled to −190° C the three alloys poor in tin were much more magnetic.
5. Annealing produced no decided improvement.
6. The susceptibility diminishes with increase of temperature, and the critical temperatures range from 225° to 275−190° C.
8. Reannealing tends to restore the initial susceptibility of the quenched material, but has little influence on the coercive force.
9. The magnetic properties are probably due to the formation of solid solutions of certain definite concentrations.