NEW CONCEPTIONS IN SCIENCE 



The rays of the ultra-violet seem to have heal- 

 ing powers, for under their influence cancers may 

 disappear and other skin diseases be similarly 

 treated. Their rdle in nature, too, is most vital, 

 for it is these rays which in the green leaves of the 

 plant turn carbonic acid and water into sugars and 

 starches the first of these conversions of the inert 

 materials of the air and the soil into food, the first 

 step towards the organization of life. 



These ultra-violet rays go through many sub- 

 stances impervious to visible light, so that if we had 

 a race of men with eyes attuned to these rays they, 

 too, might live in rooms black as ink to us. In some 

 sense theirs, too, would be another world than ours. 



Has any one the notion that while these supra- 

 sensual domains may exist, after all, they do not 

 amount to much ? Let him construct for himself a 

 scale, that he may have a clear idea of precisely 

 how much his chief and most highly developed 

 sense, the sense of sight, really takes in. 



Waves of light are measured in millionths of a 

 millimetre that is, in units of about one-twenty- 

 five-millionth of an inch. They are called micro- 

 microns, and written with the two Greek letters 

 /I/LI, for short. One /up bears the same relationship 

 to an inch as does an inch to fifteen miles. 



The largest red rays visible measure about 810 p/u, 

 and the shortest visible violet rays are about 380 jz/u 



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