MAGNETISM. (il 



the metal is capable. It is, however, more usual to employ the 

 process called the double touch : placing two magnets, witli their 

 opposite poles near to each other, or the opposite poles of a single 

 magnet, bent into the form of a horse.shoe, in contact with the mid. 

 die of the bar ; the opposite actions of these two poles then conspire 

 in their effort to displace the magnetic iluid, and the magnets having 

 been drawn backwards and forwards repeatedly, an equal number 

 of times to and from each end of the bar, with a considerable pres- 

 sure, they are at last withdrawn in the middle, in order to keep the 

 poles at equal distances. 



Iron filings, or the scoriae from a smith's forge, when finely levi- 

 gated, and formed into a paste with linseed oil, are also capable of 

 being made collectively magnetic. A bar of steel, placed red. hot 

 between two magnets, and suddenly quenched by cold water, be. 

 comes in some degree magnetic, but not so powerfully as it may be 

 rendered by other means. For preserving magnets, it is usual to 

 place their poles in contact with the opposite poles of other magnets, 

 or with pieces of soft iron, which, in consequence of their own in. 

 duced magnetism, tend to favour the accumulation of the magnetic 

 power in a greater quantity than the metal can retain after they are 

 removed. Hence the ancients imagined that the magnet fed on 

 iron. 



A single magnet may be made of two bars of steel, with their ends 

 pressed into close contact ; and it might be expected that when 

 these bars are separated, or when a common magnet has been divided 

 in the middle, the portions should possess the properties of the re- 

 spective poles only. But in fact the ends which have been in contact 

 are found to acquire the properties of the poles opposite to those of 

 their respective pieces, and a certain point in each piece is neutral, 

 which is at first nearer to the newly formed pole than to the other 

 end, but is removed by degrees to a more central situation. In this 

 case we must suppose, contrarily to the general principles of the 

 theory, that the magnetic fluid has actually escaped by degrees from 

 one of the pieces, and has been received from the atmosphere by the 

 other. 



There is no reason to imagine any immediate connexion between 

 magnetism and electricity, except that electricity affects the conduct, 

 ing powers of iron or steel for magnetism, in the same manner as 

 heat or agitation. In some cases a blow, an increase of tempera, 

 ture, or a shock of electricity, may expedite a little the acquisitioa 



