4 THE ACTION OF PHYSICAL FORCES 



not in all probability differ very essentially from eacli 

 other. 



We know that those atoms obey certain conditions 

 -which appear to be dependent upon the influences of 

 motion, gravitation, heat, light, electricity, and chemical 

 force. These powers are only known to ns by their 

 effects ; we only detect their action by their operations 

 upon matter; and although we regard the several 

 phenomena which we have discovered, as the manifesta- 

 tions of different principles, it is possible they may be 

 but modifications of some one universal power, of which 

 these are but a few of its modes of action. 



In examining, therefore, the truths which science has 

 revealed to us, it is advantageous, for the purpose of 

 fixing the mind to the subject, that we assume certain 

 conditions as true. These may be stated in a few sen- 

 tences, and then, without wasting a thought upon those 

 metaphysical subtleties which have from time to time 

 perplexed science, and served to impede the progress of 

 truth, we shall proceed to examine our knowledge of 

 the phenomena which constantly occur around us. 



Every form, whether inorganic or organic, which we 

 can discover within the limits of human search, is com- 

 posed of atoms, which are capable of assuming, under 

 the influence of certain physical forces, conditions essen- 

 tial to the physical state of that body of which they 

 constitute a part.* The known forces, active in pro- 



* Sir Isaac Newton supposed matter to consist of hard, 

 impenetrable, perfectly inelastic atoms, 



Boscovitch regarded the constitution of matter differently. The 

 ultimate atom was with him a point surrounded by powers of infi- 

 nite elasticity. (See Dr. Robisons Mechanical Philosophy, for a 

 full explanation of the theory of Boscovitcb.) 



The view entertained by JDr. Faraday, which will be compre- 

 hended from one or two short extracts from his valuable and 

 suggestive paper, claims attention : 



"If the view of the constitution of matter already referred to be 

 assumed to be correct and I may be allowed to speak of the 



