Note 79 — APPENDIX. (continued 2)

It is well known that if a rod of iron be included in a coil of coated copper wire, on making the coil the medium of a voltaic discharge, the wire is magnetized. Agreeably to a communication from Joule, in the L. & E. Phil. Mag. & Jour. for Feb,, 1847, the bar is at the same time lengthened, without any augmentation of bulk, so that its other dimensions must be lessened in proportion to the elongation.

All these facts tend to prove that a change in the relative position of the constituent ethereo-ponderable atoms of iron accompanies its magnetization, either as an immediate cause or as a collateral effect.