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XXXI. On the Magnetism of Electro dynamic Spirals, 

 By George Gore, F.R.S.* 



I HAVE made some experiments on the influence of high 

 temperatures upon the magnetic condition of electrody- 

 namic spirals formed of iron, copper, and platinum, the heat 

 being obtained by means of a voltaic battery. 



Experiment 1. — Two horizontal spirals of wire, A and B, fig. 1, 



Fis. 1. 



were employed. A was composed of a platinum wire 34*9> cen- 

 tims. long and 1*42 millim. thick, and B of a copper wire 34*9 

 centims. long and 2'5'9 millims. thick — each being coiled into a 

 cylindrical helix about 3*8 centims. long and 1*6 centim. in dia- 

 meter, with exactly the same number of turns in each ; they 

 were united by means of binding-screws, C. A magnetized 

 steel needle, D, about 8 centims. long, was suspended in the di- 

 rection of north and south (by means of a fibre about 35 or 40 

 centims. long), with its south pole between and equidistant from 

 the ends of the two coils, which were about 3 centims. asunder; 

 the needle was weighted at its centre by a little piece of lead. 

 One of the wires was coiled in the direction of a right-handed, 

 and the other of a left-handed screw, so that on passing the cur- 

 rent through them the magnetism excited in their ends nearest 

 to the needle was of the same kind ; and the direction of the 

 current was such that the poles of the wires were of the same 

 kind as that of the nearest end of the needle. With ten Grove's 

 cells as one series, the platinum plates of which were 16*5 cen- 

 tims. long and 7'7 centims. wide, the platinum wire became very 

 hot, but not red-hot, whilst the copper wire remained cold ; the 

 needle remained equidistant between the two wire poles, being 

 equally repelled by the hot platinum and cold copper. 



* Communicated by the Author. 



