id2 GENERAL SCIENCE 



means for its transmission. There must be a medium by 

 which it can pass through that vast extent of space between 

 earth and sun which is supposed to be destitute of matter. It 

 is quite impossible to conceive energy transmitted from one 

 place to another without a medium for its transmission. It 

 is supposed, and it is just a supposition, that such a medium 

 does exist. It is, however, wholly unknown to us through the 

 senses, and so cannot be matter. By supposing it to exist, 

 and attributing to it certain properties, all phenomena of 

 -the transmission through space of heat, light, and electricity 

 can be accounted for. Their transmission occurs just as if 

 such a medium did exist, and belief in its existence is as 

 assured as though it were a material medium that could be 

 weighed and handled. As a belief this is much the same as 

 when we assert that a person has a mind, or that he possesses 

 the sense of sight, because he acts just as if such were the case. 

 By making this supposition the behavior of the individual 

 can be explained and interpreted in a way wholly impossible 

 otherwise. 



Somewhat as sound waves are transmitted outward from 

 any source by the air or other material medium so we may 

 conceive a succession of pulsations in the medium known 

 as ether. Whether these wave motions manifest themselves 

 to us as heat, light, or electricity depends upon their number 

 per second reaching us, i.e., upon their wave frequency. It is 

 to be remembered, too, that not only may bodies upon which 

 these ether waves fall absorb the motions and become 

 heated thereby, but these waves may be reflected, or they 

 may be transmitted into the spaces beyond. 



SUMMARY 



Work is done when bodies are moved, and when any change in 

 motion occurs in the body as a whole or in its molecules. Both the 

 work accomplished and the effort expended in doing the work are 

 measured in the same units and theoretically are equal in amount. 



