20 MATTER AND ITS PHYSICAL PROPERTIES. 



we speak of " bodies," we mean those things, whatever they be, which excite 

 in our minds certain sensations ; and the powers to excite those sensations are 

 called " properties," or " qualities." 



To ascertain, by observation, the properties of bodies, is the first step toward 

 obtaining a knowledge t>f nature. Hence man becomes a natural philosopher 

 the moment he begins to feel and to perceive. The first stage of life is a state 

 of constant and curious excitement. Observation and attention, ever awake, 

 are engaged upon a succession of objects new and wonderful. The large re- 

 pository of the memory is opened, and every hour pours into it unbounded 

 stores of natural facts and appearances, the rich materials of future knowledge. 

 The keen appetite for discovery, implanted in the mind for the highest ends, 

 continually stimulated by the presence of what is novel, renders torpid every 

 other faculty, and the powers of reflection and comparison are lost in the in- 

 cessant activity and unexhausted vigor of observation. After a season, how- 

 ever, the more ordinary classes of phenomena cease to excite by their novelty. 

 Attention is drawn from the discovery of what is new, to the examination of 

 what is familiar. From the external world the mind turns in upon itself, and 

 the feverish astonishment of childhood gives place to the more calm contem- 

 plation of incipient maturity. The vast and heterogeneous mass of phenomena 

 collected by past experience is brought under review. The great work of com- 

 parison begins. Memory produces her stores, and reason arranges them. 

 Then succeed those first attempts at generalization which mark the dawn of 

 science in the mind. 



To compare, to classify, to generalize, seem to be instinctive propensities 

 peculiar to man. They separate him from inferior animals by a wide chasm. 

 It is to these powers that all the higher mental attributes may be traced, and 

 it is from their right application that all progress in science must arise. With- 

 out these powers, the phenomena of nature would continue a confused heap of 

 crude facts, with which the memory might be loaded, but from which the in- 

 tellect would derive no advantage. Comparison and generalization are the 

 great digestive organs of the mind, by which only nutrition can be extracted 

 from this mass of intellectual food, and without which, observation the most ex- 

 tensive, and attention the most unremitting, can be productive of no real or 

 useful advancement in knowledge. 



Upon reviewing those properties of bodies which the senses most frequently 

 present to us, we observe that very few of them are essential to, and insepa- 

 rable from, matter. The greater number may be called particular or peculiar 

 qualities, being found in some bodies, but not in others. Thus the property of 

 attracting iron is peculiar to the loadstone, and not observable in other sub- 

 stances. One body excites the sensation of green, another of red, and a third 

 is deprived of all color. A few characteristic and essential qualities are, how- 

 ever, inseparable from matter in whatever state or under whatever form it 

 exist. Such properties alone can be considered as tests of materiality. Where 

 their presence is neither manifest to sense, nor demonstrable by reason, there 

 matter is not. The principal of these qualities are magnitude and impenetra- 

 bility. 



MAGNITUDE. 



Every body occupies space ; that is, it has magnitude. This is a property 

 observable by the senses in all bodies which are not so minute as to elude 

 them, and which the understanding can trace to the smallest particle of matter. 

 It is impossible, by any stretch of imagination, even to conceive a portion of 

 matter so minute as to have no magnitude. 



