OF THE 



LIGHT-HOUSES. 



above all, to explain how the different undulati 

 undergo unequal deviations at the bounding surfaces of 

 transparent bodies. 



LIGHT-HOUSES. 



In an academy of sciences, if it properly appreciate its 

 functions, the author of a discovery is never exposed to 

 the discouraging question so often addressed to him in 

 the world, of cui bono ? Here every one comprehends 

 that the animal life ought not to be the sole occupation of 

 man ; that the cultivation of his intellect, that an atten- 

 tive study of this infinite variety of animated beings, and 

 inert matter, with which he is surrounded, forms the most 

 beautiful portion of his destined pursuits. 



But besides, even if we were desirous to find nothing 

 in the sciences but the means of facilitating the reproduc- 

 tion of substances for food, of weaving with more or less 

 economy and perfection the different fabrics which serve 

 for clothing, of constructing with elegance and solidity 

 the convenient habitations in which we escape the vicis- 

 situdes of the seasons, of extracting from the bowels of 

 the earth so many metals and combustible matter, which 

 are necessary for the arts of life, of annihilating a hun- 

 dred material obstacles which oppose themselves to the 

 intercommunication of inhabitants of the same continent, 

 of the same kingdom, even of the same city, of extract- 

 ing and preparing the medicaments proper for combating 

 the numerous disorders with which our organs are inces- 

 santly threatened, the question of cui bono ? will be 

 found completely announced. Natural phenomena have 

 innumerable points of connection with each other, often 

 hidden, the discovery of which one age bequeathes to 

 another. At the moment when these relations are dis- 



