CLASSIFICATION AIDS SCIENTIFIC PROGRESS. 209 



tically. In this case the object is to place them in that 

 order in which each substance can have only one proper 

 place, and in which it can be most easily found. Most 

 plans of arranging them have the disadvantage of afford- 

 ing several places in the series in which a single substance 

 might, with nearly equal consistency, be placed, and 

 therefore making it uncertain in which of those it may 

 be found; but an order, similar in principle to that 

 adopted in the inorganic portion of the celebrated work 

 on chemistry, by Leopold Grmelin, obviates that disad- 

 vantage. It is more difficult to classify bodies in the 

 concrete sciences than in the simple ones, because each 

 mode of classification is of nearly equal scientific im- 

 portance. 



As classification is of such great value, the completion 

 of the various tables of constants in each of the physical 

 sciences and chemistry would be an important advance. 

 An immense amount of original investigation remains to 

 be made in this direction. The subject of classification 

 is ably treated in Whewell's ' Philosophy of the Inductive 

 Sciences,' Book VIII. p. 449. 



CHAPTER XXIV. 



DIFFICULTIES OF SCIENTIFIC RESEARCH. 



NOTWITHSTANDING the vast amount of knowledge which 

 remains to be discovered, it is extremely difficult to find a 

 scientific truth which is both new and important. One 

 great difficulty consists in selecting a good subject for 

 investigation. Many researches are difficult in conse- 

 quence of their abstruseness, and others on account of 



p 



