ASTRONOMICAL EXPLANATIONS. 199 



the Poles, the length of the days and their corresponding 

 nights varies according to the seasons ; that, in our northern 

 hemisphere, after the spring equinox, the days increase while 

 the nights diminish, to such an extent that, at the summer 

 solstice, 21-22 June, they attain their maximum of length 

 (and the nights their minimum), the reverse taking place 

 during the period that elapses between the autumn equinox 

 and the winter solstice. 



I remember that I learned these data when I was living 

 rooted to or anchored upon the earth; but the explanation 

 which my masters gave me was not so clear as I could have 

 wished. Their considerations on the declensions of the sun, 

 on the obliquity of the ecliptic, on the necessity of exactly 

 reducing the earth to a simple point in relation to the dis- 

 tance of the stars, to the end that the phenomena occurring 

 (rapportes) on parallel planes would be nearly identical with 

 those observed from the centre of the globe, or from a point 

 situated on its surface j all these fine things, which demanded 

 a certain faculty of geometrical intuition, left a curious vague- 

 ness of idea upon my mind. I accepted them, under the 

 influence of authority, as beyond discussion, but I was by 

 no means satisfied whenever I wished to ascertain their 

 foundation. 



But now in the regions of space everything grows simple 

 before the mind, in which, apparently, all my power of thought 

 is concentrated. 



Behold the illuminated atmosphere ; it reminds me vividly 



