Magnetism. 23 



square of the distance increases ; in this respect 

 being analogous to gravity. 



Some natural magnets are much more power . 

 ful than others; and it is remarked, that the 

 smaller possess the power of attraction in a greater 

 degree, in proportion to their size, than the larger. 

 It indeed frequently happens, that a small load- 

 stone, cut off from a large one, will lift a greater 

 weight of iron than that from which it was cut 

 off. This can only result from the large stone 

 containing a considerable portion of matter not 

 magnetic, which rather impedes the action of the 

 magnetic part than otherwise. Loadstones have 

 been found of not more than twenty or thirty* 

 grains in weight, which would lift a piece of iron 

 forty or fifty times heavier than themselves ; and 

 we even read of one of only three grains, which 

 lifted a weight of iron of seven hundred and 

 forty-six grains, that is, two hundred and fifty 

 times its own weight. 



This property, however, which is possessed 

 by the natural loadstone, it will communicate to 

 any piece of iron by only touching it ; and the 

 piece of iron thus converted into a magnet will 

 communicate it to others, and these again to other 

 iron, without losing any part of, their magnetic 

 virtue, which seems rather increased than dimi- 

 nished by action. Magnets made by being 

 touched by a loadstone, or by other iron which 

 has been touched by it, are called artificial mag- 

 nets, and are commonly sold in the shops of those 



