MAGNETISM, &c. 



THE power of the magnet. It is one of the 

 imponderable substances, and does not affect 

 irritability, sensibility, or influence chemical 

 action.* 



The Magnet. 



Aaron Hill says the ancient Greeks called the 

 loadstone \iQog Hpa/cXeta ; the later Greeks May VTJTTC 

 At0oe ; and that the latter term was properly applied 

 to a species of lapis ollaris or potstone. 



The Magnetic Needle. 



If we hang up a magnet by a thread, or allow it to 

 swim in quicksilver or place it on a small bit of wood 

 floating in water, it never comes to a state of rest 

 until one end points to the north, and the other to the 

 south. The needle or index of a compass is a pris- 

 matic piece of tempered steel, which by having been 

 rubbed on a magnet has acquired the magnetic power, 

 and which being placed on a pivot is at liberty to turn 

 in all directions. 



Degree of Attraction. 



Iron is the only substance principally attracted by 

 the magnet. The degree of magnetic attraction de- 

 pends on the strength of the magnet itself, the weight 

 and shape of the iron presented to it, the magnetic or 



* From recent experiments the last appears doubtful. 



