RETROSPECT AND PROSPECT. 



IN the foregoing chapters I have attempted to set forth 

 the chief conceptions which are contained in the scien- 

 tific literature of the nineteenth century. Upon these 

 the scientific work of that period has been founded or 

 they are the results to which its scientific reasoning 

 has led. The most important outcome of the scientific 

 work of the century does not lie in the region of 

 thought, but rather in that of practical application ; 

 and this I have only incidentally referred to. Only 

 in so far as it has reacted upon scientific thought, sug- 

 gesting or modifying scientific ideas, has it been necessary 

 to allude to it. 



My readers who have so far accompanied me may be 

 struck by one feature which indeed is characteristic of 

 scientific thought. Our survey has presented such 

 thought as broken up into a series of different aspects ; 

 and although certain connections between these aspects 

 have been occasionally pointed out, no attempt has been 

 made to combine them into one comprehensive or united 

 view. The reason for this is to be found in the nature 

 of scientific thought itself, which, proceeding by a def- 

 inite method, starts from the great variety of phenomena 

 which surround us in time and space ; the only assump- 



