PHYSICAL SCIENCE 29 



case we can examine mathematically, the closer is 

 the actual result found to conform with that pre- 

 dicted by calculation. Our imaginary mathematical 

 model seems to represent the observed mechanical 

 phenomena of Nature in a very accurate manner, 

 until, at all events, we have to take into account 

 velocities approaching that of light. 



Let us now examine this picture or model of Nature 

 which mechanical science presents to our eyes. 



In watching any motion we are conscious of two 

 main perceptions : those of space and time. The 

 moving body describes a certain length of path and 

 takes a certain time to do so a time which our mind 

 measures in terms of its sequence of consciousness. 

 Length and Time, then, are taken as fundamental 

 concepts of the mind, corresponding to the direct 

 sense-perceptions of space and time. 



From these fundamental concepts, others follow, 

 The Velocity of the moving body is measured by the 

 length moved over in a given time, or, writing the 

 result in the initial letters as symbols, 



L 



V= T 



Again, if the velocity vary from instant to instant, 

 its change in unit time gives its rate of change, that 

 is, the acceleration of the moving body. Hence 



L 



