MATTER AND ITS PHYSICAL PROPERTIES. 19 



MATTER & ITS PHYSICAL PROPERTIES. 



PLACED in the material world, man is continually exposed to the action of 

 an infinite variety of objects by which he is surrounded. The body, to which 

 the thinking and living principles have been united, is an apparatus exquisitely 

 contrived to receive and to transmit these impressions. Its various parts are 

 organized with obvious reference to the several external agents by which it is 

 to be affected. Each organ is designed to convey to the mind immediate notice 

 of some peculiar action, and is accordingly endued with a corresponding sus- 

 ceptibility. This adaptation of the organs of sense to the particular influences 

 of material agents, is rendered still more conspicuous when we consider that, 

 however delicate its structure, each organ is wholly insensible to every influ- 

 ence except that to which it appears to be specially appropriated. The eye, 

 so intensely susceptible of impressions from light, is not at all affected by those 

 of sound ; while the fine mechanism of the ear, so sensitively alive to every 

 effect of the latter class, is altogether insensible to the former. The splendor 

 of excessive light may occasion blindness, and deafness may result from the 

 roar of a cannonade ; but neither the sight nor the hearing can be injured by 

 the most extreme action of that principle which is designed to affect the other. 



Thus the organs of sense are instruments by which the mind is enabled to 

 determine the existence and the qualities of external things. The effects 

 which these objects produce upon the mind through the organs, are called 

 sensations, and these sensations are the immediate elements of all human 

 knowledge. MATTER is the general name that has been given to that sub- 

 stance which, under forms infinitely various, affects the senses. Metaphysi- 

 cians have differed in defining this principle. Some have even doubted of its 

 existence. But these discussions are beyond the sphere of mechanical phi- 

 losophy, the conclusions of which are in no wise affected by them. Our in- 

 vestigations here relate, not to matter as an abstract existence, but to those 

 qualities which we discover in it by the senses, and of the existence of which 

 we are sure, however the question as to matter itself may be decided. When 



