The Philosophical magazine; a journal of theoretical, experimental and applied physics . stly,the flannel was well varnished. By these precautions the in-jurious effects of radiation, and especially of convection of heatin consequence of the impact of air at great velocities of rota-tion, were obviated to a great extent. The small compound electro-magnet was now put into thetube, and the terminals of its wire, lipped with platinuui, werearranged so as to dip into the mercury of a connnutator*,consislinir of two semicircular {grooves cut out of tlie base ofthe frame, fig. 1. By means of wires c
The Philosophical magazine; a journal of theoretical, experimental and applied physics . stly,the flannel was well varnished. By these precautions the in-jurious effects of radiation, and especially of convection of heatin consequence of the impact of air at great velocities of rota-tion, were obviated to a great extent. The small compound electro-magnet was now put into thetube, and the terminals of its wire, lipped with platinuui, werearranged so as to dip into the mercury of a connnutator*,consislinir of two semicircular {grooves cut out of tlie base ofthe frame, fig. 1. By means of wires connected with the mer-cury of the commutator, I could connect the revolving electro-magnet with a galvanometer or any other apparatus. In the first experiments I employed two electro-magnets(formerly belonging to an electro-magnetic engine) for thepurpose o^ inducing the magneto-electricity. They weresituated with two of their poles on opposite sides of the revol-ving electro-magnet, and the other two joining each otherbeneath the frame. I have cUawn fig. 2 representing these Fig. electro magnets by themselves, to prevent confusing fig. iron of which they were m;ule was one yard six incheslong, three inches broad, anfl half an inch thick. The wirewhich was wound upon them was ,7j^th of an inch thick ; it wasarrangetl so as to form a sixfold conductor a hundred yardslong. The following is the method in which my experiments wereniatle: — Having removed the revolving piece from its |)lace(which is done with gr(!at facility bv lifting the top ol the frame,and with it the brass socket in which the upjier steel pivot ofthe revolving piece works), I filled the tube containing thesmall compound electro-magnet with f)^ oz. of water. Alter • I had mailx- previous experiments in order to ascertain the best formof coninuitator, but found none to answer my purpose as well as tl)e found an advantai^e in covering; the mercury with a little \\ater Thesteadiness of the nee
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