354 COSMOS. 



explored, we shall be vividly impressed with the idea that the 

 solar system, especially in the great mutual connection 

 ^evealed to us during the last ten years, yields the richest 

 image of the evident and direct relations borne by many 

 cosmical bodies to a special one. 



The more limited sphere of the planetary system affords by 

 its very limitation undoubted advantages, both as to the 

 certainty and correctness of the facts ascertained by measur- 

 ing and calculating astronomy, over the results of a contempla- 

 tion of the heaven of the fixed stars. Many of these results 

 are only connected with contemplative astronomy, through 

 tne medium of stellar swarms and nebulous groups, as well 

 as of the insecurely-based photometric arrangement of the 

 stars. The most certain and brilliant portion of astrognosy 

 is the determination of positions by right ascension and 

 declination, a department of astronomical science that has 

 been very extensively improved and increased in our own 

 day, in reference to isolated fixed stars, double stars, stellar 

 masses, and nebulse. Equally difficult, although more or less 

 accurately measureable relations likewise present themselves- 

 in the proper motion of the stars the elements from which 

 their parallaxes are determined telescopic star-gatiging 

 which leads us to the distribution in space of cosmical bodies 

 the periods of variable stars and the slow revolution of 

 double stars. That which from its very nature is not amena- 

 ble to measurement, such as the relative position and con- 

 figuration of starry strata or rings of stars, the arrangement 

 of the universe, and the effects of powerfully metamorphic 

 physical forces* in the sudden appearance or extinction of 

 the so-called new stars, excites the mind the more deeply and 



1 On the appearance of new stars, and their subsequent 

 Usayuearance, jee pp. 204-222 



