214 LIGHT, VEGETATION AND CHLOROPHYLL 



considered as infinite, but we are not ready to use it. Atomic 

 energy represents a capital that we have scarcely used up to 

 the present except for destruction, but atomic piles will soon 

 be capable of producing electricity and we can hope to draw 

 plentifully from this fund which appears to be nearly 

 inexhaustible. 



Cosmic energy, from which the tides and the geothermal 

 energy of our planet proceed, is a capital which is still almost 

 intact and even in using the tides we are not breaking into it, 

 since this energy is lost every day as it aimlessly combs our 

 shores. 



Solar energy is practically the only form that has been 

 employed up to the present. We have not yet used the thermal 

 energy of the earth's surface or of the sea, but we have captured 

 the energy of water torrents. The energy from the sun trans- 

 forms the water into vapour which, losing some of its energy, 

 falls as snow or rain on the mountains whence it descends 

 to the plains, using its kinetic energy to erode the slopes and 

 carry away the soil. The energy of this descending water is 

 captured and, by means of turbines, is used to provide 

 electricity in the place of the formerly useless or destructive 

 erosion. 



More effective than turbines, chlorophyll transforms the 

 energy of the sun into living matter, if one can describe as 

 such the material which enters into the life cycle and without 

 which life would not exist. In the depths of the geological 

 strata the products of its work, ages ago, have accumulated, 

 constituting valuable reserves although they are devitalized 

 and unusable for the internal needs of the living organism. 

 The modem age exploits coal and petroleum with a thought- 

 lessness that will soon be quaUfied as criminal, for is it not, 

 to say the least, absurd to use for heating material which, 

 owing to the enormous progress of organic chemistry, is 

 capable — uniquely capable — of so many other uses? Irreplace- 

 able capital is thus being squandered every day! 



We come then to the essential energy, on which alone 

 devolves the task of maintaining hfe, on which the whole of 



