ELEMENTARY TREATISE 



MECHANICS. 



Preliminary Remarks and Definitions. 



1. MATTER has been variously defined by philosophers, 

 and some have even doubted whether we can be morally certain 

 of its existence. It is not our intention, nor does it belong to the 

 nature of our subject, to enter into discussions of this kind. Re- 

 lying solely upon experiment, we give the name of matter or body, 

 to whatever is capable of producing, through our organs, certain 

 determinate sensations ; and the power of exciting in us these 

 sensations, constitutes for us so many properties, by which we 

 recognise the presence of bodies. But among these properties, 

 two only are absolutely essential in order to our having a per- 

 ception of matter. These are extension and impenetrability, of 

 which the sight and touch are the first judges. 



2. The character derived from exte'nsion is self-evident; 

 when we see or touch a body, this body, or, if you please, the 

 power which it has of affecting us, resides in a certain portion of 

 space. The place which it occupies is therefore determinate ; 

 and by this very circumstance it is extended. 



3. When we pass our hands over the surface of a body, we 

 perceive that the matter of which it is composed, is without us ; 

 moreover, two distinct portions of matter can never be made to 

 coincide, or identify themselves, the one with the other, in such 

 a manner that the same absolute points of space shall at the 

 same time give us the sensation of both. In this consists the 

 property of impenetrability. 



