British Association for the Advancement of Science. 305 



tirely occasioned by the action of the sun's rays upon the vast body 

 of icy and snowy plains and mountains which surround the poles." 



On an (economic Application of Electro-magnetic Forces to manufac- 

 turing Purposes. By Robert Mallet. 



The separation of iron from brass and copper filings, &c, in 

 workshops, for the purpose of the refusion of them into brass, is 

 commonly effected by tedious manual labour. Several bar or 

 horse-shoe magnets are fixed in a wooden handle, and are 

 thrust, in various directions, through a dish or other vessel contain- 

 ing the brass and iron turnings, &c.,and when the magnets have be- 

 come loaded with iron it is swept off from them by frequent strokes 

 of a brush. This is an exceedingly troublesome and inefficacious 

 process. 



It appeared to the author that a temporary magnet of great power, 

 formed by the circulation of an electric current round a bar of iron, 

 might be substituted advantageously. The following is the arrange- 

 ment which he has adopted. Several large round bars of iron are 

 bent into the form of the capital letter U, each leg being about six 

 inches long. They are all coated with coils of silk-covered wire* 

 in the usual way of forming electro-magnets of such bars, and are 

 then arranged vertically, at the interval of five or six inches from 

 each other. 



All the wires from these coils are collected into one bundle at 

 their respective poles, and there joined into one by soldering, a large 

 wire being placed in the midst of them and amalgamated. A gal- 

 vanic battery is provided, which, if care be taken in making the 

 junctions at the poles, &c, need not exceed four or at most six 

 pairs of plates, of from twenty inches to two feet square. The poles 

 of this terminate in cups of mercury, which are so placed that the 

 large terminal wires of all the coils can be dipped into them, cr 

 withdrawn easily. 



The rest of the arrangement is purely mechanical. The required 

 motions are taken from any first mover, usually a steam engine. 

 The previously described arrangement being complete, a chain of 

 buckets is so contrived as to carry up and discharge over the top of 

 the magnets a quantity of the mixed metallic particles : most of the 

 iron adheres to the magnets, while the so far purified brass falls into 

 a dish or tray placed beneath to receive it. This latter is also one 

 of a chain of dishes, the horizontal motion of which is so regulated 

 that the interval between two dishes is immediately under the mag- 

 nets, in the interval of time between two successive discharges of 

 the mixed particles on the bars. 



At this juncture the communication between the galvanic battery 

 and the magnets is interrupted by withdrawing the wires from the 

 cups of mercury, and the result is, that the greatest part of the ad- 

 hering iron drops off and falls in the space between the two dishes. 

 The next dish now comes under the magnets, the communication is 



Third Series. Vol. 7. No. 40. Oct. 1835. 2 R 



