200 PROGRESS OF SCIENCE IN THE CENTURY. 



Both the Herschels, Struve, Proctor, and others 

 sought to explain the appearance of this majestic 

 way of light as due to perspective effect or optical 

 projection, but there seems to have been a complete 

 acceptance of " the more simple and direct view, 

 that the Milky Way is a definite and complicated 

 structure, and that its bifurcation, its vacuities, its 

 gaps, and its other irregularities, are definite physi- 

 cal facts." * 



The great " Bonn Durchmusterung " compiled 

 (1859-1862) under the supervision of Argelander, 

 the more recent Harvard catalogue by Pickering, and 

 Gould's list of the stars visible from the southern 

 hemisphere, illustrate supreme patience and care- 

 fulness, but as yet we remain unaware of any 

 securely established or intelligible generalisations 

 as to the stellar distribution. The Bonn list in- 

 cludes 324,198 stars down to a certain (9.5) mag- 

 nitude (estimated in terms of brightness), but mere 

 number does not impress the imagination, especi- 

 ally since the sight of the starlit sky suggests le- 

 gions upon legions of luminaries visible to the un- 

 aided eye, a suggestion very far from the truth. 

 The more impressive aspect is that which remains 

 vague, of which, indeed, we have as yet only sug- 

 gestions, that there is probably a system of the stars, 

 hidden from our gaze not only by distance, but by 

 its inherent complexity. 



A quotation from one of the modern masters may 

 serve to suggest the present tentative position: 

 " The heavens are richly but very irregularly in- 

 wrought with stars. The brighter stars cluster into 

 well-known groups upon a background formed of an 

 enlacement of streams and convoluted windings and 

 * Fison, Recent Advances, 1898, p. 85. 



