394 



SCIENCE 



[N. S. Vol. XXXVI. No. 926 



duction of artificial colors and dyestuffs. 

 The scope of studies on this subject ought 

 not to be limited to preserving colors from 

 fading, bleaching and all changes produced 

 by light. The photochemistry of colors and 

 dye-stuffs ought to furnish new methods of 

 preparation and of dyeing. Very encour- 

 aging experiments have already been made 

 with diazoic compounds and mention should 

 be made of the recent observation of Baud- 

 isch that a-nitrosonaphthylhydroxylamine 

 is changed on the fiber to azoxynaphthalene 

 when exposed to light. The autoxidation 

 of leuco compounds by light is an old prac- 

 tise of which the ancients availed them- 

 selves for preparing pvirple ; now the proc- 

 ess is explained, thanks to the familiar re- 

 searches of Friedlander, but it is clear that 

 a great deal remains to be learned in this 

 field. 



Phototropie substances, which often as- 

 sume very intense colors in the light, and 

 afterwards return in the darkness to their 

 primitive color, might be used very effec- 

 tively. Such substances might well attract 

 the attention of fashion rather than 

 fluorescent materials which give the im- 

 pression of changing colors. The dress of 

 a lady, so prepared, would change its color 

 according to the intensity of light. Pass- 

 ing from darkness to light the colors would 

 brighten up, thus conforming automatically 

 to the environment: the last word of fash- 

 ion for the future. 



Solar energy is not evenly distributed 

 over the surface of the earth; there are 

 privileged regions, and others that are less 

 favored by the climate. The former ones 

 would be the prosperous ones if we should 

 become able to utilize the energy of the 

 sun in the way which I have described. 

 The tropical countries would thus be con- 

 quered by civilization, which would in this 

 manner return to its birthplace. Even 



now the strongest nations rival each other 

 in the conquest of the lands of the sun, as 

 though unconsciously foreseeing the future. 

 Where vegetation is rich, photochemistry 

 may be left to the plants and by rational 

 cultivation, as I have already explained, 

 solar radiation may be used for industrial 

 purposes. In the desert regions, unadapted 

 to any kind of cultivation, photochemistry 

 will artificially put their solar energy to 

 practical uses. 



On the arid lands there will spi'ing up 

 industrial colonies without smoke and with- 

 out smokestacks; forests of glass tubes will 

 extend over the plains and glass buildings 

 will rise everywhere; inside of these will 

 take place the photochemical processes that 

 hitherto have been the guarded secret of 

 the plants, but that will have been mastered 

 by human industry which will know how 

 to make them bear even more abundant 

 fruit than nature, for nature is not in a 

 hurry and mankind is. And if in a distant 

 future the supply of coal becomes com- 

 pletely exhausted, civilization will not be 

 checked by that, for life and civilization 

 will continue as long as the sun shines ! If 

 our black and nervous civilization, based 

 on coal, shall be followed by a quieter civili- 

 zation based on the utilization of solar 

 energy, that will not be harmful to progress 

 and to human happiness. 



The photochemistry of the future 

 should not however be postponed to such 

 distant times; I believe that industry will 

 do well in using from this very day all the 

 energies that nature puts at its disposal. 

 So far, human civilization has made use 

 almost exclusively of fossil solar energy. 

 Would it not be advantageous to make 

 better use of radiant energy? 



GlACOMO ClAMICIAN 



