Page:Proceedings of the Royal Society of London Vol 60.djvu/318

292 Table I.—Table of Results of Observations on the Magnetic Permeability of Liquid Oxygen.

A - primary current, in amperes, passing through, primaries of the transformer and balancing coil. 8*037 28*13 37'8 36*8 50*5 Corresponding mean magnetising force in C.Gr.S. units in primary circuit of transformer. Total ballistic throw which would be produced if primary current of A amperes were reversed through primary of transformer alone = A. a Ballistic throw of galvanometer resulting from immersion of the transformer in liquid oxygen. Transformer and balancing induction coil being opposed = D. permeability calculated from a

35-2 1734 4-33 1 1 -00250 123 0 6068 14-9 1 -00246 165-4 8153 21 -18 1 -00260 161 -0 7938 23-57 1 -00297 220 -9 10894 32-98 1 00304

The values of the permeability given in the foregoing table are not all of equal weight.

The calculated value of fi—1 depends upon the observed ballistic throw, and this cannot be read to a high degree of accuracy when the throw is as small as 4 millimetres. We consider that the best result is obtained by taking the mean of the values for the primary currents, 37-8, 36-8, and 505 amperes, and these values give fi = 1-00287, with a probable accuracy of ± 0-0002. This value of the permeability of the liquid oxygen corresponds to a magnetising force lying between 166 and 220 C.G.S. units. It will be seen that this method is best applicable to the determination of the permeability under large magnetising forces ; and that these observations do not, in themselves, allow us to state whether the permeability is a constant for all forces, or is a function of the value of the force. In the next place the value is a relative one. The number 1-00287 is the ratio of the magnetic permeability of liquid oxygen to that of the gaseous oxygen nearly at the same temperature resting upon the surface of the liquid. We were not able by this method to detect the difference between the permeability of the cold gaseous oxygen lying on the surface of the liquid oxygen when in quiet ebullition, and which has a temperature of about -182° C., but a density of at least three times that of oxygen at 0° C., when compared with that of gaseous oxygen at ordinary temperature, and under the normal pressure. In a very valuable memoir on the determination of magnetic susceptibilities, M. P. Curie* has examined the susceptibility of gaseous

Docteur es Sciences Physiques,’ par M. P. Curie, Paris, 1895.’ This memoir is of remarkable interest in many ways.
 * ‘ Theses presentees a la Faculte cles Sciences de Paris pour obtenir le grade de