HIS HISTORY OF ASTRONOMY. 117 



the opposite point of view, and reflect on the extreme 

 feebleness of the natural means by the help of which so 

 many great problems have been attacked and solved ; if 

 we consider that to obtain and measure the greater part 

 of the quantities now forming the basis of astronomical 

 computation, man has had greatly to improve the most 

 delicate of his organs, to add immensely to the. power of 

 his eye ; if we remark that it was not less requisite for 

 him to discover methods adapted to measuring very long 

 intervals of time, up to the precision of tenths of seconds ; 

 to combat against the most microscopic effects that con 

 stant variations of temperature produce in metals, and 

 therefore in all instruments ; to guard against the innu 

 merable illusions that a cold or hot atmosphere, dry or 

 humid, tranquil or agitated, impresses on the medium 

 through which the observations have inevitably to be 

 made ; the feeble being resumes all his advantage ; by 

 the side of such wonderful labours of the mind, what 

 signifies the weakness, the fragility of our body; what 

 signify the dimensions of the planet, our residence, the 

 grain of sand on which it has happened to us to appear 

 for a few moments ! 



The thousands of questions on which Astronomy has 

 thrown its dazzling light belong to two entirely distinct 

 categories ; some offered themselves naturally to the 

 mind, and man had only to seek the means for solving 

 them ; others, according to the beautiful expression of 

 Pliny, were enveloped in the majesty of nature ! When 

 Bailly lays down in his book these two kinds of problems, 

 it is with the firmness, the depth, of a consummate 

 astronomer ; and when he shows their importance, their 

 immensity, it is always with the talent of a writer of the 

 highest order; it is sometimes with a bewitching elo- 



