TN an earlier paper the author 1 has studied the Hall effect in iron, •*-nickel and cobalt at a number of temperatures between -190 0 and 1100 0 C. For a given magnetic field the Hall effect in these metals was found to increase more and more rapidly, until the critical temperature of the metal in question was reached, where for a small additional increase in temperature the effect sinks suddenly to a small fraction of its value at that temperature and then continues to decrease with further

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... e of temperature. In each of these metals it is known that there is a molecular change at the critical temperature. The nickel changes from a-nickel to /3-nickel; the iron from a-iron to /3-iron and then to 7-iron; and the cobalt from a-cobalt to /3-cobalt. These molecular transformations manifest themselves also in a change of the electrical resistance, 2 in a change of the thermoelectric heights 3 and in a change in the magnitude of the Peltier effect. 4 These latter changes are, however, not large in comparison with the change in the Hall effect or with the change in the permeability. This behavior of the Hall effect at the critical temperature allies it more closely to the magnetic properties of the metal than to either the resistance or the thermoelectric heights. It seemed of interest to examine some of the other effects which are allied to the Hall effect, in order to see in what way they are influenced by changes of temperature and by the molecular transformations which are known to take place when the metals pass from the magnetic to the non-magnetic state. For a clear statement of the various phenomena which arise when a metal plate which is carrying either a current of heat or a current of electricity is brought into a magnetic field so that the lines of force are normal to the plane of the plate, reference is made to the paper by H. Zahn 5 and to the paper by Hall and Campbell 6 on these phenomena. For our present purposes it is only necessary to recall that when a metal 1