New Magtietic Electrical Machine. 165 



adjusted by milled head screws, e, is the pulley wheels and /, 

 the multiplying wheel, g, the top board, is secured to the frame 

 by screws, and answers as a convenient table for experiment. 

 The magnets are sixteen inches long, the armatures ten inches, 

 so that the whole machine occupies but little room. The alter- 

 nating currents, from the semi-revolutions of the armatures, are 

 converted into a current of the same direction, by the application 

 of niy pole changer. This simple contrivance, beautifully appli- 

 cable to the magneto-electric, as well as to the electro-magnetic 

 machine, will be found fully described in Vol. xxxiii. No. 1. p. 190, 

 of this Journal. It consists merely of two insulated, metallic, 

 cylindrical segments, secured on the shaft, and two stationary 

 metallic tangent springs for conductors. Silver, about the purity 

 of coin, answers best. The wires from each of the armatures, 

 pass through holes in the brass straps, and through openings in 

 the sides of the machine, to be attached to the pole changers, one 

 of which is seen at h. One pole changer would suffice for both 

 armatures, but by using two, the experiments may be considera- 

 bly varied, as the separate coils may be combined, to form a sim- 

 ple or compound battery, i i, are the tangent springs of copper, 

 but tipped with silver where they rest upon the silver pole chan- 

 ger. They pass up through the top board of the machine, and 

 are soldered respectively to the brass straps k k, into which are 

 screwed the mercury cups, one of which is of glass for exhibiting 

 the spark, combustion of ether, alcohol, oil, «fcc. These cups rep- 

 resent the two constant poles of the revolving coils. The circuit 

 is completed and broken by the rise and fall of the curved wire 

 m, attached to the little lever /. At /, the lever is pulled down by 

 a spiral spring. At the other end is fastened a string, which 

 passes down to the lower lever, n. This is worked by the re- 

 volving pins n s, attached to a movable ferule on the shaft. 

 The pins n s, are themselves binding screws, so that the ferule 

 may be adjusted in any position, and the circuit broken at any 

 required time. This electrotome, as it may be called, is removed 

 when decompositions are performed, and the platinum wires are 

 inserted into the mercury cups. The machine works equally 

 well, turned either way. I have not yet had opportunity to 

 measure the rate of decomposition of pure water, but it is certainly 

 as rapid as from one hundred pairs of galvanic plates. Pure wa- 

 ter is rapidly decomposed when the platinum wires are ten inches 



