YI. MAGNETISM. 



MAGNETISM, as was proved by the important discov- 

 ery of Faraday, will produce electricity ', but with this 

 peculiarity that in itself it is static ; and, therefore, to pro- 

 duce a dynamic force, motion must be superadded to it : it is, 

 in fact, directive, not motive, altering the direction of other 

 forces, but not, in strictness, initiating them. . It is difficult 

 to convey a definite notion of the force of magnetism, and of 

 the mode in which it affects other forces. The following il- 

 lustration may give a rude idea of magnetic polarity. Sup- 

 pose a number of wind-vanes, say of the shape of arrows, 

 with the spindles on which they revolve arranged in a row, 

 but the vanes pointing in various directions : a wind blowing 

 from the same point with an uniform velocity will instantly 

 arrange these vanes in a definite direction, the arrow-heads 

 or narrow parts pointing one way, the swallow-tails or broad 

 parts another. If they be delicately suspended on their spin- 

 dles, a very gentle breeze will so arrange them, and a very 

 gentle breeze will again deflect them ; or, if the wind cease, 

 and they have been originally subject to other forces, such as 

 gravity from unequal suspension, they will return to irregu- 

 lar positions, themselves creating a slight breeze by their re- 

 turn. Such a state of things will represent the state of the 

 molecules of soft iron ; electricity acting on them not indeed 

 in straight lines, but in a definite direction produces a polar 



