22 Experimental Philosophy. [Lecture 3. 



is diffused through all nature. In a part of Vir- 

 ginia there is a magnetic sand, the grains of 

 which exhibit all the properties of larger load- 

 stones, and indeed are loadstones in miniature. 



The great and distinguishing property of the 

 magnet is its attraction for iron; and this at- 

 traction is mutual between them. Thus, if a 

 magnet and a piece of iron are placed each of 

 them on a small piece of wood, in a bason or 

 tub of water, so as to float on the surface, (see 

 Plate II. fig. 4.) the magnet will approach the 

 iron as well as the iron the magnet; and if either 

 of them is held steady, the other will move to- 

 wards it. Muschenbroek, by a series of experi- 

 ments, endeavoured to ascertain the degree of 

 force with which a magnet would attract at dif- 

 ferent distances. He suspended a magnet two 

 inches long, and sixteen drachms in weight, to 

 one of the scales of an accurate balance, and 

 under it he placed a bar of iron, while the 

 weights were put in the opposite scale. 



At 6 inches it attracted 8 grains. 



5 - - 31 



4 4i 



3 - - 6 



2 - - 9 



1 - 18 



And in contact 87 



From subsequent experiments, it has been 

 proved that the magnetic force diminishes as the 



