700 EXPEKIMENTS ON AMPERE'S LAWS. 



are parallel and in the same direction, and therefore 

 attract each other. Arrangements for exhibiting ex- 

 clusively the mutual effect of intersecting currents are 

 rather complicated. 



When the current is only permitted to traverse the 

 movable conductor, or the fixed conductor is so far 

 removed from it that it cannot exert any sensible in- 

 fluence, a further phenomenon may be observed, which 

 will be explained further on, in the article on magnetism. 

 The square will begin to move as soon as it is traversed 

 by the current, and place itself in a fixed position, with 

 its plane passing nearly from east to west, or more 

 exactly east-north-east to west- south- west, so that the 

 current ascends on the western side of the square and 

 descends on the side turned towards the east. 



C. Electro-magnetism. Magnetism. Induction by 

 Currents. 



51. Electro -magnetism. An insulated copper wire is 

 coiled round a glass tube in close turns, forming two 

 or more layers of wire, and covering a little more than 

 half the length of the tube, as shown in fig. 353. A 



FIG. 353 (real size}. 



small bar of iron, somewhat longer than the uncovered 

 part of the tube, which is closed at the end by a cork, 

 is placed within the tube, the end a being in contact 

 with the cork and the end b reaching to some distance 

 within the coil. When a strong current is sent through 



