The Evolution of the Sciences 



First, we have the nebulae. They appear 

 to us like milky white clouds, with ill-defined 

 edges, sometimes condensed in a certain number 

 of brighter regions, looking like stars sur- 

 rounded by an aureole. Some, irregular in 

 shape, are surrounded in all directions by a 

 coma of whitish filaments; others take the form 

 of flattened globules which are visible at times 

 on edge, at others askew or flat. 



The number of the nebulae is considerable; 

 at present more than eight thousand have been 

 counted, and new ones are discovered every 

 year. An American astronomer alone, Mr 

 Swift, has catalogued nearly a thousand; at 

 the Paris observatory M. Bigourdan has under- 

 taken to determine the exact position of all 

 these nebulae and already several thousands 

 have been accurately located. 



At what distance from us do these cosmic 

 masses gravitate? They appear to be at the 

 ends of the world. In any case it has hitherto 

 been impossible to determine the parallax 

 of a single one, and the diffused appearance 

 of their contour would render a determination 



of this nature particularly difficult. But M, 



238 



