has been standing in a vacuum vessel for any length of time has a composition which varies with the time and which may contain aa much as 75 or 80 per cent, of oxygen, it was not to be expected that very closely consistent results could be obtained in the case of air. The following figures show, however, the observational results :—
Permeability of Liquid Air.
Throws of Ballistic Galvanometer. Induction Coils balanced.
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1 '5 mm. to right T The transformer in liquid air. Exp. I. -j 1 ‘2 „ „ > Current = 38 '0 amperes reversed through L 1 ‘1 „„ J primary coils. Exp. II. Exp. III. ~| The transformer lifted out of liquid air into 17 "0 mm. to left I cold gaseous air at the same temperature 17 '5 „ „ f as before. 37 "5 amperes reversed. 0 -3 mm. to right 1 The transformer in liquid air. Q. Current = 37 amperes reversed through J primary coils. Exp. IV. Later. r i J 17 *0 mm. to left 17*0 „ 17 -3 „ Exp. Y. 2 *8 mm. to left 2-8 „ Exp. VI. f 18 ‘8 mm. to left 19-2 „ 19-4 „ 19-8 „
The transformer lifted out of liquid air into cold gaseous air, and at the same tempera-
- ture as before.
Current = 37 amperes reversed through J primary coils. 1 The transformer in liquid air. r Current = 36*7 amperes reversed through J primary coils. The transformer lifted out of liquid air into J cold gaseous air, at the same temperature y as before. j Current = 37 amperes reversed through J primary coils. Exp. VII. { 3 *5 mm. to left 3-4 „ 22 *0 mm. to left Exp. V III. <{ 22 *0 „ „ 22-0 „ 1 The transformer in liquid air. V Current = 36 -7 amperes reversed through J primary coils. j The transformer in liquid air. j Primary circuit of balancing coil cut out of circuit and 0T118 ampere reversed through j primary of transformer to standardise the J ballistic galvanometer.
The results of these observations, when reduced, show that corresponding to a primary current of 37'5 amperes, or a mean magnetising orce of 164 C.G.S. units, the apparent magnetic permeability of liquid air in terms of gaseous air of the same temperature is 1-00240.
