6 SCIENTIFIC THOUGHT. 



and modern times a convenient resting-place ; but the 

 repose which it afforded has never been long enjoyed ; 

 every new attempt to attach permanent, ultimate, or 

 intrinsic properties to matter, or to its particles, has pro- 

 voked the desire to explain these properties by going still 

 farther back, and to see in them, through the dissecting 

 microscope of the mind's eye, a still more hidden motion. 

 Two of the most suggestive ideas by which physical 

 science has benefited in the nineteenth century are the 

 successful explanation of the dead pressure of gases by 

 a rapid translational, and of the rigidity of solid bodies 

 by a rapid rotational, motion of matter. The second 

 of these suggestions is far from being exhausted in its 

 capabilities ; the working out of the ultimate problems 

 which it suggests will be one of the principal tasks of 

 the coming age. 

 2. The kinetic view of nature, however useful and suggest- 



Descartes' 



develop- ive it may have shown itself to be in recent times, did not 



meiit of 



view*' 116 *' yi e ld any fruits of real knowledge either in the hands of 

 the ancients or even in those of the first great philoso- 

 pher of modern times, in those of Descartes. Just like 

 attraction and atomism, the kinetic theory had to be 

 worked out by the instruments of measurement and calcu- 

 lation, by the exact method, before it led to any actual 

 results. The kinetic view of nature was made scientifi- 

 cally possible when Newton, in the First Book of the 

 ' Principia,' laid down for all time the laws of motion. 

 And yet we can hardly say that Newton himself developed 

 this promising vein of exploration ; for, even while open- 

 ing out an endless vista of research, he also, in the enun- 

 ciation of the so-called law of gravitation, afforded only 



