408 MAGNETISM. 



compound magnet, to act more powerfully upon a 

 piece of steel. 



Various processes have been employed for this 

 purpose ; the following may suffice. 



Place two magnetic bars, AB (Plate 21. fig. 

 16.), in a line with the north, or marked end of 

 one, opposed to the south, or unmarked end of 

 the other, but at such a distance from each other, 

 that the magnet to be touched may rest with its 

 marked end on the unmarked end of A, and its 

 unmarked end on the marked end of B; then 

 apply the north end of the magnet D, and the 

 south end of E, to the middle of the bar C, the 

 opposite ends being elevated as in the figure ; draw 

 D and E asunder along the bar C, one towards A, 

 the other towards B, preserving the same eleva- 

 tion ; remove D and C a foot or two from the bar 

 when thev are off the ends, then bring the north 

 and south poles of these magnets together, and 

 apply them again to the middle of the bar C as 

 before ; repeat the same process five or six times, 

 then turn the bar, and touch the opposite surface 

 in the same manner, and afterwards the two re- 

 maining surfaces; by this means the bar will 

 acquire a strong fixed magnetism. 



The following is also recommended by Cavallo : 



Place the two bars which are to be touched 

 parallel to each other, and then unite the ends by 

 two pieces of soft iron, called supporters, in order 

 to preserve, during the operation, the circulation 

 of the magnetic matter ; the bars are to be placed 

 so that the marked end D (Fig. 17-) may be op- 

 posite the unmarked end B ; then place the two 

 attracting poles G and I on the middle of one of 

 the bars to be touched, raising the ends, so that 

 the bars may form an obtuse angle of 100 or 120 



