ON MAGNETISM. GQS 



iron or steel ; that end assumes in some degree the opposite character, and 

 the opposite end the same character: but in drawing the pole along the bar, 

 the first end becomes neutral, and afterwards has the opposite polarity; while 

 the second end has its force at first a little increased, then becomes neutral, 

 and afterwards is opposite to what it first was. When the operation is re- 

 peated, the effect is at first in some measure destroyed, and it is difficult to 

 understand why the repetition adds materially to the inequality of the distri- 

 bution of the fluid ; but the fact is certain, and the strength of the new mag- 

 net is for some time increased at each stroke, until it has acquired all that it 

 is capable of receiving. Several magnets, made in this manner, may be placed 

 side by side, and each of them being nearly equal in strength to the first, 

 the whole collection will produce together a much stronger effect; and in this 

 manner we may obtain from a weak magnet others continually stronger, until 

 we arrive at the greatest degree of polarity of which the metal is capable. It is, 

 however, more usual to employ the process called tlie double touch : placing 

 two magnets, with their opposite poles near to each other, or the opposite poles 

 of a single magnet, bent into the form of a horseshoe, in contact with the 

 middle of the bar: the opposite actions of these two poles then conspire in 

 their effort to displace the magnetic fluid, 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 pressure, they are at last with- 

 drawn in the middle; in order to keep the poles at equal distances. 



Iron filings, or the scoriae from a smith's forge, when finely levigated^, 

 and formed into a paste with linseed oil, are also capable of being made col- 

 lectively magnetic. A bar of steel, placed red hot between two magnets, and 

 suddenly quenched by cold water, becomes in some degree magnetic, but no4: 

 so powerfully as it may be rendered by other means. For preserving mag- 

 nets, 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 nietal can retain after they are removed. Hence 

 the ancients imagined that the magnet fed on u"on. 



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

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