188 GENERAL CONDITIONS OF SCIENTIFIC RESEARCH. 



pure science itself.' 1 The principle of orderly development 

 from the evident to the -obscure is also manifested in the 

 evolution of inventions and arts as well as in that of dis- 

 coveries ; for instance, the system of counterpoint in music 

 was not developed until the sixteenth century, nor the art 

 of orchestration until the eighteenth ; and the art of 

 scientific discovery is still later. 



Without attempting to discuss the extent and value of 

 the evidence in support of such a logical order, it is evident 

 that if such an order exists it must greatly affect our most 

 general views of the relations of the various sciences, and 

 of the forces of which they treat. If also this view is 

 correct, that most of the general principles and laws of 

 each science in the series, operate in a more or less modified 

 form in all the succeeding sciences, a knowledge of it must 

 afford us some idea of discoveries yet to be made, and con- 

 stitute an important source of new and truthful hypotheses. 

 For example, if the general principles which operate in the 

 sciences of light and heat, operate also in those of electri- 

 city and magnetism, we may expect to discover sooner or 

 later that these latter forces are compound and may be 

 decomposed, also that they possess the properties of radia- 

 tion and absorption, modified and disguised by other con- 

 ditions. The theory of c electric and magnetic images and 

 shadows ' supports this hypothesis. If also all the prin- 

 ciples of the elementary sciences are but simpler forms of 

 those of the more complex ones, then physiological actions 

 will be found to be due to physical and chemical changes. 

 The present state of physiological knowledge also strongly 

 supports this view. 2 



1 Tait, Recent Advances of Physical Science, p. 2. 



2 A more extensive exposition of the chronological order of dis- 

 covery, and the conditions which govern it, may be found in First 

 Principles, by Herbert Spencer, part ii. chapter i. 



