OF NATURAL PHILOSOPHY. 329 



physical research ; one, however, which has of late 

 begun to be studied with a diligence which promises 

 the speedy disclosure of relations and laws of which 

 at present we can form but a very imperfect notion. 



(367.) The communication of magnetism from the 

 earth to a magnetic body, or from one magnetic body 

 to another, is performed by a process to which the 

 name of induction has been given, and the laws and 

 properties of such induced magnetism have been 

 studied with much perseverance and success, prac- 

 tically, by Gilbert, Boyle, Knight, Whiston, Cavallo, 

 Canton, Duhamel,Rittenhouse,Scoresby, and others; 

 and theoretically, by jiEpinus, Coulomb, and Poisson, 

 and in our own country by Messrs. Barlow and 

 Christie, who have investigated with great care the 

 curious phenomena which take place when masses 

 of iron are presented successively, in different posi- 

 tions, by rotation on an axis, to the influence of the 

 earth's magnetism. The magnetism of crystallized 

 bodies (partly from the extreme rarity of such as are 

 susceptible of any considerable magnetic virtue) has 

 not hitherto been at all examined, but would probably 

 afford very curious results. 



(368.) To electricity the views of the physical 

 enquirer now turn from almost every quarter, as to 

 one of those universal powers which Nature seems 

 to employ in her most important and secret oper- 

 ations. This wonderful agent, which we see in 

 intense activity in lightning, and in a feebler and 

 more diffused form traversing the upper regions of 

 the atmosphere in the northern lights, is present, 

 probably in immense abundance, in every form of 

 matter which surrounds us, but becomes sensible 



