344 FRAGMENTS OF SCIENCE. 



with the rest, changing, it is true, from age to ago, 

 but changing without break of continuity in the rela- 

 tion 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 

 various parts are taken up by different minds, and thus 

 receive a greater amount of attention than could pos- 

 sibly 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 

 individuals, each of whom directs his efforts, more or 

 less, along a single line. Accepting, in many respects, 

 his culture from his fellow-men taking it from spoken 

 words or from written books in some one direction, 

 the student of Nature 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 im- 

 part. 



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 gen- 

 erally, 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 phenomena and laws of magnetism 

 and electricity with those of sound with the pres- 

 sures and motions of liquids and gases, whether at rest 

 or in a state of translation or of undulation. The sci- 



