To the Editors of the Philosophical Magazine and Journal. GENTLEMEN

The publication, in your December Number, of a memoir by Mr Chrystal on Bi- and Unilateral Galvanometer Deflection recalled to my mind some observations of a like character made some years ago by myself. I have lately succeeded in finding the manuscript of a communication with the above title read (literally) before the British Association at Norwich in 1868, which contains a short account of these observations. As the subject has acquired an additional interest in consequence of the investigations of Dr Schuster and Mr Chrystal, I shall be glad if you can find room for my paper, which has not been printed in full hitherto.

I am, Gentlemen,

Your obedient Servant,

Rayleigh.

The following paper contains a short account of some experiments which led to rather unexpected results, of which I can find no notice in the methodical treatises on Electricity, although they might seem to be in the way of any experimenter on induced currents. The arrangement of the first experiment was nearly the same as that described by Faraday in his original memoir on induction. Two thick copper wires were coiled together the circuit of one being completed by the battery and make-and-break apparatus, and that of the other by an ordinary astatic galvanometer of moderate sensitiveness. The make-and-break arrangement is a very rude one of my own construction, acting either by the dipping of needles into mercury, or by the intermittent contact of a spring with a toothed wheel.