CHAPTER III 



The Sun and Climatic Variation 



AFTER giving birth to our planet the sun continued to be 

 so closely linked with it, as with the other planets also, 

 that the more we increase our knowledge of those links the 

 more they justify the worship it has inspired in diverse forms 

 in so many of the peoples of antiquity. From the sun our 

 earth, in addition to its material constitution, received and 

 retains both its inner heat and the movements which cause it 

 to revolve on its own axis and ceaselessly describe its vast 

 elliptical orbit. From these movements night and day and 

 the regular succession of the seasons take their existence, 

 manifestations of the tutelage in which we are still held 

 subject by the father of stars — held chained, indeed, by the 

 mysterious bond of attraction within his resplendent mantle 

 of gold and purple radiance. 



Nothing takes place on our earth without the intervention of 

 the sun. It penetrates the waters of the sea, scattering their 

 molecules till they become invisible and then draws them up 

 into the air, where they are left to unite and form clouds. 

 It is the sun that, by heating unequally the different regions of 

 the earth, generates the moisture-laden winds whence fall the 

 fertilizing rains that permitted life to appear on the 

 continents. And it is the sun that induces in the living web 

 of the plant's texture the chlorophyll, the green substance 

 which, when activated by its rays, combines water with 

 carbonic acid and liberates the oxygen consumed by animals, 

 thus performing the miracle of producing sugar and starch. 

 These are called by the chemists carbo-hydrates, because they 

 are composed entirely of water and carbon, and constitute 

 the first and only source of all food, whether for animal or 

 plant. 



The sun alone, therefore, can maintain life on the earth. It 

 determines the conditions of its development equally on land 

 and sea. Innumerable green microscopic algae float on the 

 surface of the sea in calm and clear weather ; and at the bidding 



