30* Dr. Faraday's Researches in Electricity. [Series xix. 



that an electric current would give the same result of action 

 on light as a magnet; and* in the helix, would supply a form 

 of apparatus in which great lengths of diamagnetics, and 

 especially of such bodies as appeared to be but little affected 

 between the poles of the magnet, might be submitted to exa- 

 mination and their effect exalted: this expectation was, by 

 experiment, realized. 



2190. Helices of copper wire were employed, three of which 

 I will refer to. The first, or long helix, was 0'4< of an inch 

 internal diameter ; the wire was 0'03 of an inch in diameter, 

 and having gone round the axis from one end of the helix to 

 the other, then returned in the same manner, forming a coil 

 sixty-five inches long, double in its whole extent, and con- 

 taining 1240 feet of wire. 



2191. The second, or medium helix, is nineteen inches long, 

 1*87 inch internal diameter, and three inches external dia- 

 meter. The wire is 02 of an inch in diameter, and eighty feet 

 in length, being disposed in the coil as two concentric spirals. 

 The electric current, in passing through it, is not divided, but 

 traverses the whole length of the wire. 



2192. The third, or Woolwich helix, was made under my 

 instruction for the use of Lieut.-Colonel Sabine's establish- 

 ment at Woolwich. It is 26*5 inches long, 2'5 inches inter- 

 nal diameter, and 4*7.5 inches external diameter. The wire 

 is 0*17 of an inch in diameter, and 501 feet in length; It is 

 disposed in the coil in four concentric spirals connected end 

 to end, so that the whole of the electric current employed 

 passes through all the wire. 



2193. The long helix (2190.) acted very feebly on a mag- 

 netic needle placed at a little distance from it; the medium 

 helix (2191.) acted more powerfully, and the Woolwich helix 

 (2192.) very strongly ; the same battery of ten pairs of Grove's 

 plate being employed in all cases. 



2194. Solid bodies were easily subjected to the action of 

 these electro-helices, being for that purpose merely cut into 

 the form of bars or prisms with flat and polished ends, and 

 then introduced as cores into the helices. For the purpose 

 of submitting liquid bodies to the same action, tubes of glass 

 were provided, furnished at the ends with caps; the cylindri- 

 cal part of the cap was brass, and had a tubular aperture for 

 the introduction of the liquids, but the end was a flat glass 

 plate. When the tube was intended to contain aqueous fluids, 

 the plates were attached to the caps, and the caps to the tube 

 by Canada balsam ; when the tube had to contain alcohol, 

 aether or essential oils, a thick mixture of powdered gum with 

 a little water was employed as the cement. 



2195. The general effect produced by this form of appa- 



