MAGNETISM. 



pregnatcd, however abundantly, with the 

 magnetic principle, if it be heated or 

 hammered, the power of attraction will 

 be dissipated ; or if a tube filled with 

 iron filings have their surface magnetised, 

 by shaking the tube the magnetic influ- 

 ence will likewise be lost. In some re- 

 spects, the magnetic influence resembles 

 caloric ; for it very rapidly communicates 

 to iron, devoid of magnetism, a certain 

 portion of its own powers ; which, how- 

 ever, appear to be reproduced instanta- 

 neously. As various small fires under 

 one large vessel will thereby heat it, and 

 cause the water it contains to boil, though 

 either of them individually would not 

 produce that effect ; so many weak mag- 

 nets may, by causing each to communi- 

 cate a power equal to its own, be made 

 to create an accumulated power, larger 

 than that contained by either of them in- 

 dividually : there is, however, a seeming 

 contradiction to be found in some au- 

 thors, who recommend that the weakest 

 magnets should be first applied, and those 

 more forcible in succession, according to 

 the power they may possess ; the reason 

 assigned being, that the weaker magnets 

 would else, in all probability, draw off 

 some of the accumulated power from the 

 new magnet. Of this there appears no 

 danger, since experience proves that 

 magnets rather gain than lose efficiency 

 by contact, not only with each other, but 

 even with common iron. In fact, the 

 magnetic power mav at any time be cre- 

 ated by various means : the friction of 

 two pieces of flat and polished bars of 

 iron will cause them for a short while to 

 attract, and to suspend, light weights. 

 Soft iron is more easily influenced, but 

 steel will retain the influence longer. 

 Lightning, electricity, and galvanism, be- 

 ing all of the same nature, equally render 

 iron magnetic. It is also peculiar, that 

 when two or more magnets are left for 

 any time with their several north poles in 

 contact, the whole will be thereby weak- 

 ened ; whereas, by leaving a piece of 

 common iron attached to a magnet, the 

 latter will acquire strength. It is also 

 well known, that some pieces of steel 

 quickly receive the magnetic influence, 

 while others require considerable labour, 

 and after all are scarcely impregnated. 

 The oxide of iron cannot be impregnated, 

 and those bars that have been so, when 

 they become partially oxydized, lose their 

 power. Hence we see "the necessity of 

 preserving the needles of compasses 

 from rust. 



Magnets have the power to act, not- 

 withstanding the intervention of substan- 



ces in any degree porous between them, 

 and the body to be acted upon : thus, if a 

 needle be put on a sheet of paper, and a 

 magnet be drawn under it, the needle 

 will follow the course of the magnet. 

 The peculiar affinity of the load-stone for 

 iron is employed, with great success, by 

 those who work in precious metals, for 

 the separation of filings, &c. of iron from 

 the smaller particles of gold, 8cc. A mag- 

 net being dipped into the vessel, in which 

 the whole are blended, will attract all fer- 

 ruginous particles. 



To communicate the magnetic power 

 to a needle, let it be placed horizontally, 

 and with a magnet in each hand, let the 

 north pole of one, and the south pole of 

 the other be brought, obliquely, in contact 

 over the centre of the needle ; draw them 

 asunder, taking care to press firmly, and 

 preserving the same angle or inclination 

 to the very ends of the needles, which 

 should be supported by two magnets, 

 whose ends ought to correspond in pola- 

 rity with those of the needle. Observe to 

 carry the magnets you press with clear 

 away from the ends of the needle, at least 

 a foot therefrom ; repeat the friction in the 

 same manner several times, perhaps six, 

 eight, or ten times, and the needle will be 

 permanently magnetized. As we have 

 already stated, by using other magnets in 

 succession, the powers of the needle will 

 be proportionably increased. But no ef- 

 fect will result from the friction if the 

 bars are rusty, or, indeed, not highly 

 polished; their angles must be perfect, 

 and their several sides and ends com- 

 pletely flat. 



It is, perhaps, one of the most curious 

 of the phenomena attendant upon this 

 occult property, that the centre of every 

 magnet is devoid of attraction ; yet, that 

 when a needle is placed in a line with a 

 magnet, and within the influence of its 

 pole, that needle also becomes magnetic ; 

 or, rather, a conductor, possessing a cer- 

 tain portion of attractive power : and it is 

 no less extraordinary, that the magnet 

 retains its power even in the exhausted 

 receiver of an air-pump: this seems to be 

 a formidable objection to its being influ- 

 enced by any fluid. Perhaps the opinion 

 entertained by many of our most popular 

 lecturers on this subject, viz. that the 

 earth itself is the great attractor, may be 

 nearest the truth. We are the more sup- 

 posed to incline towards such an hvpo- 

 thesis, knowing that, at the true magne- 

 tic equator, the needle does not dip ; and 

 from the well ascertained fact, that bars 

 oi iron, placed for a length of time exactly 



