LIGHT-HOUSES. 265 
above all, to explain how the different undulations can 
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 cut 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~ 
