202 THE BOOK OF THE LANTERN. 



one of bismuth assuming the opposite direction under the 

 same conditions. This last experiment is to show the 

 difference between a magnetic and dia-magnetic body. 



But the most beautiful magnetic experiments are only 

 possible with a vertical attachment fitted to the lantern. 

 Obtain a couple of flat bar magnets two inches in length. 

 Place one of these in the centre of the horizontal stage, and 

 focus sharply on the screen. The appearance is that of a 

 thick black bar. Now sift through a muslin bag some iron 

 filings, so that the screen appears covered with black spots. 

 Tap the stage with the finger nail, so as to disturb the 

 particles of iron, and they will be seen to gather round the 

 poles of the little magnet, and to form the beautiful magnetic 

 curves. A still more striking experiment may be per- 

 formed with two magnets so placed that their poles of 

 opposite names, N. and S., face one another, while they 

 are at the same time about one inch apart. Now scatter 

 the filings as before, and the effect of the graceful curves 

 embracing one another between the two poles is simply 

 magnificent. Remove the magnets, wipe the filings from 

 the stage, and once more arrange the bars in the same 

 position, but with poles pf the same name facing one 

 another. When the filings are now scattered over the 

 magnets, a great contrast to the last experiment is apparent. 

 Where just now all was harmony, there is visible antago- 

 nism. " Poles of opposite name attract one another, and of 

 the same name repel one another." And this repulsion is 

 most beautifully shown. The curves no longer embrace 

 one another, but meet and turn back upon themselves, 

 forming a line of confusion where the meeting takes 



