88 THE PROGRESS OF SCIF.N n 



attempts to prognosticate the course of scientific 

 progress. 



I have pointed out that the growth of clear and 

 definite views respecting the constitution of 

 matter has led to the conclusion that, so far as 

 natural agencies are concerned, it is ingenerable 

 and indestructible. In so far as matter may be 

 conceived to exist in a purely passive state, it is, 

 imaginably, older than motion. But, as it must 

 -<umed to be susceptible of motion, a particle 

 of bare matter at rest must be endowed with the 

 potentiality of motion. Such a particle, however, 

 by the supposition, can have no energy, for there 

 is no cause why it should move. Suppose now 

 that it receives an impulse, it will begin to move 

 with a velocity inversely proportional to its mass, 

 on the one hand, and directly proportional to the 

 strength of the impulse, on the other, and will 

 possess kinetic energy, in virtue of which it will 

 not only continue to move for ever if unimpeded, 

 but if it impinges on another such particle, it will 

 impart more or less of its motion to the latter. 

 Let it be conceived that the particle acquires a 

 tendency to move, and that nevertheless it does 

 not move. It is then in a condition totally different 

 from that in which it was at first. A cause com- 

 jH-t.Mit to produce motion is operating upm it. but. 

 for some reason or other, is unable to u r i\v rise to 

 unit i. HI. If the obstacle is removed, the energy 

 which was there, but could not manifest itself, at 



