IDENTICAL CHANGES 



in passing through aggregations of matter of dif- 

 ferent density. Evidently, then, the light does not 

 merely pass through the holes, but the intervening 

 matter undergoes a change because of the light. 

 Then every identity undergoes a change, under the 

 influence of light, that is different from the change 

 that any other identity undergoes, therefore is light 

 the first and foremost impression; therefore, we 

 receive the sense of outline, of color, size and tex- 

 ture. 



What, then, is the difference between transparent 

 body and the body not transparent? Upon all of 

 them alike the pressure of a given beam of light is 

 exerted. And the change produced by light is on 

 the surface only, of the reflecting body, and turns 

 to heat in the interior of the opaque body, while 

 the transparent body transmits the change, pro- 

 duced on the surface, to every subdivision of the 

 body, and from the last particle again to an adja- 

 cent body that repeats the process or to void mat- 

 ter. The popular conception of light is, that the 

 vibrations producing it are identical in frequency 

 and extent. And in its own nature, that is, in the 

 length and rapidity of the waves, it is already di- 

 vided into the colors of the spectrum before it acts 

 on any material body. And yet light is not and 

 cannot be anything more than a mechanical dis- 

 placement of void matter between one celestial 

 body and another in space. And that void matter, 

 whatever we may choose to call it, does not possess 

 the power to acquire momentum. So one wave 

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