Page:Proceedings of the Royal Society of London Vol 60.djvu/313

Rh the transformer and the one on the balancing induction coil, were connected in opposition to one another through a sensitive ballistic galvanometer in such a manner that on reversing the primary current the galvanometer was affected by the difference between the electromotive forces set up in the two secondary coils, and a very fine adjustment could be made by moving in or out the adjusting coil of the balancing induction coil.

The arrangement of circuits is shown in fig. 2.

Magnetic Permeability of Liquid Oxygen and Liquid Air. 287 Fig. 2.

Arrangement of the Circuits of the Transformer and Induction Coil. For the purpose of standardising the ballistic galvanometer employed, the primary coil of the balancing induction coil could be cut out of circuit, so that the inductive effect in the ballistic galvanometer circuit was due to the primary current of the closed circuit transformer alone. A resistance box was also included in the circuit of the ballistic galvanometer. The resistance of the ballistic galvanometer was about IS ohms, and the resistance of the whole secondary circuit 30'36 ohms. The experiment then consisted in first balancing the secondary electromotive forces in the two coils exactly against one another, then immersing the transformer in liquid oxygen, the result of which was to disturb the inductive balance, and in consequence of the magnetic permeability of the liquid oxygen core being greater than unity, a deflection of the ballistic galvanometer was observed on reversing the same primary current. The induction