144 On the Laxvs of Symmeb-y^ 



of nature must result. According to this view, then, the specific 

 forms of crystalline bodies are to be viewed as the result of con- 

 spiring or antagonist forces, one of which is of a general charac- 

 ter, and ever tending to a constant effect ; the others, of parti- 

 cular characters, taking their rise in particular circumstances, 

 and tending to particular effects. 



By adopting such a view, then, the study of crystallography 

 may be assimilated to analogous branches of physical science. 

 In mechanical philosophy, for instance, it is usual to analyze phe- 

 nomena by referring them to two or more forces, one of which is 

 regarded as of a determinate and general nature, and denomi- 

 nated a law of nature ; while the other is usually regarded mere- 

 ly as a peculiar pressure or impulse, deriving its origin from 

 some special circumstance, and acting, to a certain extent, as an 

 antagonist to the law of nature, and modifying the result which 

 would ensue were the latter to take effect alone. Thus, in 

 analyzing the planetary motions, it is usual to view them as the 

 result of the combined action of the law of gravitation, on the 

 one hand, and of a particular impulse, on the other, modifying 

 the result which would speedily ensue were gravitation by itself 

 to take effect upon the planetary bodies. In philosophising on 

 the descent of a heavy body, in like manner, it is usual to 

 ascribe its fall to the same law of gravitation, and to account 

 for its shortcomings in fulfilling that law by the resistance of the 

 air as an antagonist element. Now, although, according to the 

 understanding of all philosophers (I should hope), the law of 

 gravitation be merely viewed as a general announcement in terms 

 of space and time of the phenomena themselves, (though it is 

 vulgarly believed to account for them) ; and though that be but a 

 mioced philosophy which is contented to view a phenomenon as 

 the resultant of two such incommensurable factors, as an ab- 

 stract idea and a material body (as, for instance, when we as- 

 cribe the fall of a heavy body to gravitation on the one hand, 

 and to the pressure of the air on the other), still this is a mode of 

 viewing phenomena which is possessed of many advantages. 

 By its aid the powers of mathematical science can be very ad- 

 vantageously applied to physics ; by its use the mind, when 

 seeking gratification to its curiosity, is led away from the inven- 

 tion of hypothesis; and, until the natural mechanism is disco- 

 vered by which attraction, repulsion, rotation, and revolution 



