ON THE PROPERTIES OF MATTER, Ike, 



SB 



admiration of the virtuous and the excellent. That he did not feel the 

 force of any argument offered by nature in proof of the immortahty of the 

 soul, and was in this respect considerably below the standard of Socrates 

 and Cicero, must be equally aduiitted and lamented ; and should teach us 

 the high value of that full and satisfactory light which was then so much 

 wanted, and has since been so gloriously shed upon this momentous subject. 

 But let it at the same time be remembered, that, with a far bolder front 

 than either of the philosophers here adverted to, he dared to expose the 

 grossness and the absurdities of the popular religion of his day, and in his 

 life and his doctrines gave a perpetual rebuke to vice and immorality of 

 every kind. And hence, indeed, the main ground of the popular calumny 

 with which his character was attacked, and which has too generally ac« 

 companied his memory to the present day. 



LECTURE IV. 



ON THE PR0PER;riES OF MATTER, ESSENTIAL AND PECULIAR, 



In our last lecture I endeavoured to render it probable, that all visible 

 or sensible matter is the result of a combination of various solid, impene- 

 trable, and exquisitely fine particles or units of the same substance, too 

 minute to be detected by any operation of the senses. Of the shape or 

 magnitude of these particles we know nothing : and even their sohdity and 

 impenetrability, as 1 then observed, is rather an assumption, for the- purpose 

 of avoiding several striking difficulties and absurdities that follow from a 

 denial of these qualities, than an ascertained and established fact. 



From this unsatisfactory view of it in its elementary and impalpable 

 state, let us now proceed to contemplate it in its manifest and eombined 

 forms, and to investigate the more obvious properties they offer, and the 

 general laws by which they are regulated. 



The change of distance between one material body and another, or, in 

 other words, their approach to our separation from each other, is called 

 motion ; and the wide expanse in which motion of any kind is performed 

 is denominated space. 



Matter has its essential, and its peculiar properties. Its essential 

 properties are those which are common to it under every form or mode of 

 combination. Its peculiar properties are those which only appertain to it 

 under definite forms or definite circumstances. 



The essential properties of matter are usually classed under the six 

 following heads: passivity, extension, density, impenetrability, divisibihty, 

 and gravitation ; which, however, may easily be reduced to four, since 

 extension, density, and impenetrabihty may be comprehended under the 

 general term of cohesibility. 



Passivity, inertia^ or ms inertice^ is the tendency in a body to persev-ere 

 in a given state, whether of rest or motion, till disturbed by a body of 

 superior force. And hence these terms, which are mere synonyms, imply 

 a power of mobility as well as a power of quiescence ; although passivity 

 has often been confined to quiescence, while mobility has been made a 

 distinct property. Thus it is from the same power or tendency to passivity, 

 that a cannon ball continues its motion after being projected from a gun, 

 as that by which it remained at rest before it was thrown off ; for it is 



