258 THE PRINCIPLES OF SCIENCE. 



Variable Properties of Matter. 



I have enumerated some of the few properties of matter, 

 which are manifested in exactly the same manner by all 

 substances, whatever be their differences of chemical or 

 physical constitution. But by far the greater number of 

 qualities vary in degree ; substances are more or less 

 dense, more or less transparent, more or less compressible, 

 more or less magnetic, and so on. One very common 

 result of the progress of science is to show that qualities 

 supposed to be entirely absent from many substances are 

 present only in so low a degree of intensity that the 

 means of detection were insufficient. Newton believed 

 that most bodies were not affected by the magnet at all ; 

 Faraday and Tyndall have rendered it very doubtful 

 whether any substance whatever is wholly non-magnetic, 

 including under that term diamagnetic properties. We 

 are rapidly learning to believe that there are no sub- 

 stances absolutely opaque, or non-conducting, non-electric, 

 non-elastic, non-viscous, non-compressible, insoluble, in- 

 fusible, or non- volatile. All tends to become a matter of 

 degree, or sometimes of direction. There may be some 

 substances oppositely affected to others, as ferro-magnetic 

 substances are oppositely affected to diamagnetics, or as 

 substances which contract by heat are opposed to those 

 which expand; but the tendency is certainly for every 

 affection of one kind of matter to be represented by some- 

 thing similar in other kinds. On this account one of 

 Newton's rules of philosophizing seems quite to lose all 

 validity; he said, ' Those qualities of bodies which are 

 not capable of being heightened and remitted, and which 

 are found in all bodies on which experiment can be made, 

 must be considered as universal qualities of all bodies.' 

 As far as I can see, the contrary is more probable, namely, 



