MAGNETIC INSTRUMENTS. 



Fig. 409. 



Bar Magnets. (Fig. 409.) These instruments are 

 adapted for the experimental elucidation of that peculiar 

 property conferred on bodies essentially composed of iron, 

 whereby, under certain circumstances, they acquire the 

 powers of polarity, attraction of unmagnetic iron, attraction 

 and repulsion of magnetic iron, and the influence of inducing 

 magnetism in other iron not previously magnetic. 



Price, 4 inch, 25cts. ; 6 inch, 3 Sets. 



" 8 " $0.50 and $0.75. 



" 10 " $0.75 " $1.00. 



" 12 " $1.00 " $1.50. 



Artificial Magnets (Fig. 410) made of 

 steel, are now generally used in preference 

 to the natural magnet, or loadstone, not only 

 as they may be procured with greater ease, 

 but because they are far superior to the 

 natural magnet in strength, and communi- 

 cate the magnetic virtue more powerfully, 

 and may be varied in their form more easily ; 

 the most usual of which is the bar magnet, 

 and the horse -shoe or U magnet ; the latter 

 is much the most powerful. The piece of 

 iron used to connect the poles, or extremities 

 of a horse-shoe magnet, is the armature or 

 keeper, and by being kept on the poles of the 

 magnet when not in use, preserves its power. 



Fig. 410. 



