ELEMENTARY MAGNETISM 363 



of physical powers become more and more manifest: until 

 he is finally led to regard Nature as an organic whole as 

 a body each of whose members sympathizes with the rest, 

 changing, it is true, from age to age, but changing with- 

 out break of continuity in the relation of cause and effect. 



The system of things which we call Nature is, how- 

 ever, too vast and various to be studied first-hand by any 

 single mind. As knowledge extends there is always a 

 tendency to subdivide the field of investigation. Its vari- 

 ous parts are taken up by different minds, and thus re- 

 ceive a greater amount of attention than could possibly 

 be bestowed on them if each investigator aimed at the 

 mastery of the whole. The centrifugal form in which 

 knowledge, as a whole, advances, spreading ever wider 

 on all sides, is due in reality to the exertions of individ- 

 uals, each of whom directs his efforts, more or less, along 

 a single line. Accepting, in many respects, his culture 

 from his fellow-mentaking it from spoken words or from 

 written books in some one direction, the student of Nat- 

 ure ought actually to touch his work. He may otherwise 

 be a distributor of knowledge, but not a creator, and he 

 fails to attain that vitality of thought and correctness of 

 judgment which direct and habitual contact with natural 

 truth can alone impart. 



One large department of the system of Nature which 

 forms the chief subject of my own studies, and to which 

 it is my duty to call your attention this evening, is that 

 of physics, or natural philosophy. This term is large 

 enough to cover the study of Nature generally, but it 

 is usually restricted to a department which, perhaps, lies 

 closer to our perceptions than any other. It deals with 

 the phenomena and laws of light and heat with the phe- 



