XII. New instrument for continuously recording the strength and direction of a varying electric current
R. Shida · The London Edinburgh and Dublin Philosophical Magazine and Journal of Science · 1886
I ENCLOSE herewith a paper which I have just drawn upand which is a description of a new instrument I have devised and constructed for continuously recording the streng.thand direction of a varying electric cm'rent.My chief aim m designing such an instrument was to use it for making observations of both regular and irregular variations of earthcurrents which are present in the telegraph-wires of this country, just as they are present in the telegraph-wires of any other country.The importance of carrying on careful observations of earth-currents has been felt more and more since you showed it before the Society of Telegraph Engineers and Electricians~ about eleven years ago, in your presidential address.Indeed, so great an importance is now attached to such observations, that it was one of the main subjects discussed by the International Electric Congress which met at Paris last year.Now, since both regular and irregular earth-currents are so variable, that their strength and direction change, not only from day to day, but from hour to hour, or from minute to minute, or even from second to second, observations will be of very little value unless they are continuously made; hence the importance of a method of continuously registering the strength and direction of varying electric currents.The photographic method, such as is used in the Kew Observatory, is, of course, very satisfactory and accurate.But this method, besides requiring an elaborate arrangement of several pieces of apparatus, has a serious disadvantag% namely, that the observations must be made in a dark room.I have therefore felt for a long time the want of a method which, though not so accurate as the photographic method, is simple and convenient.It was thus that I was led to devise the apparatus described in the accompanying paper.As will be seen from the description given in the paper, the galvanometer-part of the apparatus is, in the main, the same as that of the more recent one of your Siphon Recorders ; that is to say, a cell containing a great number of turns of fine wire is suspended in a strong magnetic field produced by