SECTION III. 



DISTRIBUTION OP THE STARS IN SPACE. 



BEFORE the invention of the telescope, it was impossible 

 to acquire a very precise knowledge of the distance of 

 the stars and their distribution in space ; and even after 

 the invention of the telescope, no one attempted to use it 

 in any adequate manner to determine the constitution of 

 the heavens, until the time of Sir William Herschel. This 

 astronomer, having the command of instruments far supe- 

 rior to any who had preceded him, undertook a series of 

 exact observation, upon which to found a knowledge of 

 the starry heavens. In 1784 he first advanced an hypo- 

 thesis respecting the Milky Way, which was substantially 

 as follows : The stars of our firmament, instead of being 

 scattered in all directions indifferently through space, con- 

 stitute a cluster with definite limits, in the form of a 

 stratum, of which the thickness is small in comparison 

 with its length and breadth; and in which the earth 

 occupies a space somewhere about the middle of its thick- 

 ness, and . near the point where it subdivides into two 

 principal laminae, inclined at a small angle to each other. 

 For, to an eye so situated, the apparent density of the 

 stars, supposing them pretty equally scattered through the 



