328 M. Arago on Nebuloe. 



ing to him, compose the celestial vault, are united or soldered 

 together. The extravagance and absurdity of these concep- 

 tions is a reason for giving more prominence to a thought of 

 Democritus, again brought forward and illustrated by Ma- 

 nilius, which presents so much that is subtile, ingenious, and 

 difficult to discover. According to these philosophers, if the 

 Milky Way shines with a lively lustre, it is because the stars 

 in it are too close upon each other for us to see them, con- 

 sidering their prodigious distance, one by one ; it is because 

 the images of so many stars greatly condensed are confounded 

 with each other. 



Opinions of the Moderns : Galileo^ IVriglit^ Kant^ Lambert. — 

 As soon as he directed one of his earliest telescopes towards 

 the heavens, Galileo discovered multitudes of new stars. The 

 sixth magnitude ceased to be the last limit of visibility. The 

 belt and sword of Orion, in which the Greek and Arabian 

 astronomers could count only eight of these stars, exhibited to 

 him upwards of eighty. The Pleiades exhibited thirty-six to 

 him, instead of the six or seven of the ancients. The Milky 

 Way presented distinct stars, where nothing before had ever 

 been seen but confused lights. Thus, Galileo again revived 

 the explanation of Democritus ; but supporting it by precise 

 observations, he brought it out, to a certain point, from the 

 domain of mere conjecture. Ever since it has been almost 

 generally adopted. 



The explanation of Democritus and Manilius left entirely 

 aside circumstances, not less worthy of the attention of astro- 

 nomers than are the light and whiteness of the Milky Way : 

 I speak of WxQform of the phenomenon, its continuity, and the 

 almost perfect coincidence of its principal branch with one 

 of the great circles of the sphere. A coincidence so singu- 

 lar, a continuity so astonishing, cannot be the effect of chance ; 

 these are two things which cannot but have physical causes. 

 The investigation, the profound study of these causes, seems 

 to have been a predominating object with Herschel. It is in 

 the form, in the position of the Milky Way, considered al- 

 ways as an agglomeration of stars, that the illustrious astro- 

 nomer conceived that he had discovered the secret of the con- 

 stniction of the heavens. 



