HISTORY OF DISCOVERY RELATIVE TO MAGNETISM. 289 



cover wliether your bride had man-ied you from motives of aflPectiou or other- 

 wise. Both were to be eflPected by the mystical use of the maguet. 



It has ah-eady been meutioued that on the surface of a maguet there are two 

 points at which the attractive power manifests itself with the greatest intensitv, 

 and that these points are called poles. If a piece of soft iron is presented to 

 one of these poles, the iron itself will become a magnet of inferior power, will 

 exhibit two poles, and attract a second piece of iron ; this second piece of iron 

 will in turn become a maguet, and attract a third, and so on. The power may 

 thus be developed in a series of iron bars placed end to end, provided the original 

 magnet has considerable power. If, instead of bars of iron, small particles, 

 such as filings of iron, be placed under the influence of the magnet, they will 

 adhere together in masses, and form a kind of beard around the poles, or, if they 

 are sprinkled oil a sheet of paper placed over the magnet, they will be attracted 

 to the poles and to each other, forming curves of great regularity and beauty.* 



These experiments were known to the ancients, and Lucretius must have seen 

 them performed by the priests, since he describes them minutely in his poem 

 to which we have previously alluded. In this he states that iron filings con- 

 tained in a brass basin appeared to boil when a magnet was moved under them; 

 that a row of iron rings would hang one below the other on a magnet, and that 

 these experiments were performed by the priests in connexion with the Samo- 

 thracean mysteries. A similar experiment was exhibited at a festival held every 

 ninth year in honor of Apollo at Thebes, in Boetia, which consisted in hanging 

 one iron ball on another. These experiments were undoubtedly made by means 

 of a strong magnet inducing its power in pieces of soft iron, the^atter exhibiting 

 the attraction as long as they were in metallic contact with the former, but im- 

 mediately losing the power when the contact was severed. 



It is only when the iron has been rendered hard by hammering or twisting 

 that it is able to retain a small amount of magnetism. But if, instead of soft 

 iron, bars of tempered steel are placed in contact with the pole of a magnet, 

 they will at first not be attracted as powerfully as those of iron ; but if they 

 are allowed to remain in contact for some time, or if rubbed with the magnet, 

 they will fully acquire the magnetic property, and retain it after they have 

 been sejiarated from the inducing magnet. 



If a bar of steel, which has thus been rendered permanently magnetic, and 

 of which its poles are at its ends, be placed on a piece of cork, and allowed to 

 float horizontally on water, or if it be supported on a firm point at its centre of 

 gravity, or, still more simply, by a fine thread, so as to have free motion in 

 every direction horizontally, it will not remain at rest indifi'erently in any 

 direction, but will turn itself so as to point Avith its poles to a definite region of 

 the earth, the one to the north, and the other to the south. If two such movable 

 magnetic bars are brought near each other, the poles of both which point to the 

 north, and also those which point to the south, will repel each other, whilst the 

 pole which points to the north in the one will attract the pole which points to 

 the south in the other, and vice versa. 



The directive property of a freely suspended magnetic bar towards certain 

 points of the horizon, which is generally called the polarity of the needle, was 

 not known to western nations as early as the attractive power of the magnet 



* A very interesting experiment, which may be called the exhibition of magnetic spectres, 

 consists in tracing on a polished plate of steel, such as the blade of a wide handsaw, an image 

 in outline with a pencil, and afterwards passing slowly and with some pressure along the 

 lines of this image one of the tapered poles of a straight magnet of considerable power. If a 

 sheet of white paper is aftenvards pasted smoothly over this steel surface, and against this, 

 while it is held vertically, fine iron filings are projected from a box with a perforated cover, 

 the image will start into existence on the blank paper, as if by magic, in lines of bristling 

 fihngs. 



The image is interestingly shown by drawing a serpentine line on a long saw blade, to 

 represent a snake ; the configuration of the filings gives a peculiar effect to tins exhibition. 



19 s 



