APPENDIX 349 



very profitable, but in the present case its very possibility, if 

 even only in theory, is very important. 



Without entering into details as to the origin of other vege- 

 table substances, less important to man as compared with 

 albuminoids, we may nevertheless apply to them what has been 

 said about the albuminoids, and thus arrive at the conclusion 

 that the agency of sunlight is necessary only for the forma- 

 tion of starch or, speaking more generally, of carbohydrates 

 from carbonic acid and water ; no other substances require 

 sunlight for their formation. 



We can only now appreciate fully the significance of the pro- 

 cesses taking place in the chlorophyll granule under the action 

 of sunlight. 



In the first place, from the chemical point of view, it is here 

 that inorganic matter, carbonic acid and water, is transformed 

 into organic matter here lies the source and origin of all the 

 heterogeneous substances out of which the organic world is built 

 up. On the other hand, from the physical point of view, the 

 chlorophyll granule represents an apparatus for capturing the 

 sun's rays, which then are laid up in store for future use. 



Plants form organic matter out of the air, and stores of energy 

 out of sunlight. They represent in every respect the machine 

 invented by Mouchot and Ericsson the machine set in motion 

 by the energy of the sun, free of cost. This explains the result 

 of the farmer's labour : by expending but a comparatively small 

 amount of substance in the form of manure, he obtains great 

 masses of organic matter ; by expending a certain quantity of 

 energy he acquires great stores of it in the form of fuel and food. 

 He burns down a forest, feeds sheep on the grass of his meadows, 

 sells the corn of his fields, and yet everything returns to him 

 again in the form of air, which, under the influence of sunlight, 

 again acquires the form of forests, fields, and corn. With the 

 assistance of plants he transforms air and light which have no 

 market value into marketable quantities. He trades in air 

 and sunlight. 



These considerations dispose of the theories occasionally 

 heard concerning the fate awaiting humanity when chemists 

 shall have discovered the secret of synthesising complicated 

 organic bodies, and have found means of preparing artificial 



