Page:Proceedings of the Royal Society of London Vol 60.djvu/110

Rh Table VI.—Variation of Permeability with Temperature.

Pianoforte Steel.

Temperature measured in Platinum degrees by standard thermometer P" F e r t ilit y . Magnetic Permeability, $c., of Iron at Low Temperatures. 95'

Magnetising Magnetising

Temperature. force, 7’50. force, 2039.

- 0° 86-0 361-0 - 20 84-0 332-5 — 40 81-0 299-5 - 60 79-0 271-5 - 80 77-0 246-5 -1 0 0 74-0 220-0 -1 2 0 71-5 193-0 -1 4 0 68-5 174-3 -1 6 0 67-0 163-0 -1 8 0 66-0 153-0 -2 0 0 64-5 144-0

We pronose to continue the examination of the anomalous behaviour so presented by iron in different states of hardening by examining in the same way the changes of permeability in the case of several iron rings of the same dimensions formed in the one case of soft annealed iron, and in another case of the same quality of iron hardened, and in the remaining cases using steel of known composition at different states of temper. We desire to add that in the conduct of this research we have been under great obligations to Mr. J. E. Petavel for rendering us very efficient assistance in taking the exceedingly tedious ballistic galvanometer observations, and in reducing them when taken.