Increase of resistance of bismuth films in a magnetic field; the effect of heat treatment.—Films of bismuth one centimeter long by 3 millimeters wide were sputtered from chemically pure bismuth on glass slides to resistances varying from 25 ohms to 200 ohms. If especial care is taken to avoid heating these films during the sputtering, by allowing the process to go on intermittently at short intervals, there is little or no change produced in the resistance of such films when placed in a transverse magnetic field of 16,000 gauss. If the films are heated to a temperature near the melting point of bismuth and allowed to cool and this process repeated several times, after each heating the film exhibits a greater change of resistance in the magnetic field than before it, until a certain upper limit is reached, beyond which further heating, if the previous maximum temperature is not exceeded, has little effect. Likewise, heating to successively higher temperatures, beginning at a fairly low maximum and gradually approaching the melting point of the metal in each successive heating, restores the property under investigation to a greater and greater degree. Heating to temperatures under 150° has very little effect towards restoring this property, while heating to temperatures above this value has a correspondingly larger effect. If the film is strongly heated while being sputtered the initial increase of resistance in the magnetic field is comparatively large and further heating produces only slight increases in this initial value. The increase of resistance in weak fields or where the total effect is not large is strictly proportional to the square of the field strength.