168 ON MAGNETISM. 



SECTION IX. 



ON SUBPERMANENT MAGNETISM IN IRON SUBJECTED 

 TO MECHANICAL VIOLENCE. 



75. Primary experiment on Subpermanent Magnet- 

 ism: a long plate or slender bar of iron is placed on a 

 firm frame (sometimes called the 'Magnetic Anvil), with 

 its length parallel to the local dip, and is struck re- 

 peatedly with a hammer: it becomes a magnet, with red 

 magnetism in the end which dipped (in northern mag- 

 netic latitudes} ; and this magnetism does not change with 

 change of the magnet's position. 



It will be convenient to prepare a small frame, as 

 represented in Figure 55, of which the essential parts 



Fig. 55. 



are, one surface transversal to the direction of local dip, 



