206 M. Arago oti the Physical Constitution of the Sun. 



One may perhaps feel humiliated by a result which reduces 

 so far our position in the material world ; but consider that 

 man has succeeded in extracting everything from his own 

 resources, whereby he is elevated to the highest rank in the 

 world of thought. Astronomical examinations, then, might 

 almost excuse, on our part, some little vanity. 



Bat I must not follow modern astronomers in their im- 

 mortal peregrination through the multitude of suns which 

 shine in the firmament. 



We must first, then, see to determine, with the help of their 

 instruments, the relative position of these stars, cataloguing 

 a hundred thousand of them ; we know that Pliny the elder 

 was astonished that Hypparchus had tried to observe 1022, 

 and compared it to the work of a god. 



We would remark, that in recent w^orks of complete astral 

 catalogues, we shall find that the number of stars visible to 

 the naked eye in a single hemisphere, namely, the northern, 

 is under three thousand. A certain result, and one which, 

 notwithstanding, will strike with astonishment, on account 

 of its smallness, those who have only vaguely examined the 

 sky on a beautiful winter night. 



The character of this astonishment will change, if we pro- 

 ceed to the telescopic stars. Carrying the enumeration to 

 stars of the fourteenth magnitude, the last that are seen 

 by our most powerful telescopes, we shall find by an estimate 

 which will furnish us the minior limit, a number superior to 

 40 millions (40 millions of suns ! !), and the distance from the 

 farthest among them is such, that the light would take from 

 three to four thousand years to traverse it. 



We are, then, fully authorised to say, that the luminous 

 rays — these rapid couriers — bring us, if I may so express it, 

 the very ancient history of these distant worlds. 



A photometric experiment, of which the first indications 

 exist in the Cosmotheoros of Huygens, an experiment resumed 

 by Wollaston a short time before his death, teaches us that 

 20,000 millions of stars the same size as Sirius, the most bril- 

 liant of the firmament, would need to be agglomerated to 

 shed upon our globe a light equal to that of the sun. 



Guided by the penetrating genius of William Herschel, we 



