M. Elias 071 a simple Method of Magiiething Steel Bars. 349 



which is to be made, viz. highly powerful magnets, which is 

 rarely the case. 



With my method I require nothing more than what every 

 experimentalist possesses, and may be had everywhere, a pow- 

 erful voltaic pair and some copper wire. From twenty-two 

 to twenty-five feet of well- isolated copper wire are wound 

 round to form a hollow^ very short, but very thick cylinder 

 (see woodcut). A strong current is passed through the wire, 



and the steel bar to be magnetized is placed in the cylinder, 

 in which it is moved up and down to the very ends. When 

 the central portion of the steel bar again occupies the cylinder, 

 the circuit is opened, and the bar, which is now perfectly mag- 

 netized, withdrawn. When the bar is curved in the form of 

 a horse-shoe, it is well to close it with its keeper during the 

 magnetizing, and when a straight one, to provide it at top and 

 bottom with a piece of soft iron. The wire which I employ 

 is ^th of an inch in thickness. The thickness of the wire is 

 not at all indifferent ; the same effect it is true may be pro- 

 duced with a thinner one, but then it requires a battery of 

 greater intensity. The voltaic apparatus which I make use of 

 is a single platinum and zinc pair arranged on Grove's prin- 

 ciple; it has ^rd square foot active platinum surface; the re- 

 sistance which the current meets with in this battery is equal 

 to that of a clean copper wire, 1 millimetre in diameter and 

 |rds of a metre in length*. The experiments however suc- 

 ceed perfectly well, even when the battery presents a twice or 

 three times greater resistance. My hollow cylinder is 1 inch 

 high, the bore is nearly li inch in diameter, and its sides 

 likewise \\ inch thick. 



To test the efficiency of my magnetizing cylinder, a friend 



* Since in Grove's battery the smallness of the resistance depends not 

 merely on the size of the metallic surface, but likewise considerably on the 

 goodness of the porous earthen cell, which cannot be determined, I have 

 conceived it to be possible to indicate the power of the battery independent 

 of the resistance only in this manner. 



