246 COSMOS. 



light in all self-luminous stars (in the central body of our own 

 planetary system, and in the distant suns or fixed stars) has 

 long and justly directed attention to the importance 23 and 

 significance which attach to the periodical or non -periodical 

 variation in the light of the stars in reference to clima- 

 tology generally ; to the history of the atmosphere, or 

 the varying temperature which our planet has derived in 

 the course of thousands of years from the radiation of the 

 sun; with the condition of organic life, and its forms of 

 development in different degrees of latitude. The variable 

 star in the neck of the Whale (Mira Ceti) changes from 

 the 2nd magnitude to the llth, and sometimes vanishes 

 altogether ; we have seen that TJ Argus has increased from 

 the 4th to the 1st magnitude, and among the stars of this 

 class has attained to the brilliancy of Canopus, and almost to 

 that of Sirius. Supposing that our own sun has passed 

 through only a very few of these variations in intensity 

 of light and heat, either in an increasing or decreasing 

 ratio, (and why should it differ from other suns?) such a 

 change, such a weakening or augmentation of its light-pro- 

 cess, may account for far greater and more fearful results 

 for our own planet than any required for the explanation of 

 all geognostic relations, and ancient telluric revolutions. 

 William Herschel and Laplace were the first to agitate these 

 views. If I have dwelt upon them somewhat at length, it is 

 not because I would seek exclusively in these the solution of 

 the great problem of the changes of temperature in our earth. 

 The primitive high temperature of this planet at its forma- 

 tion, and the solidification of conglomerating matter the 



23 William Herschel, On the Changes that happen to the 

 Fixed Stars, in the Philos. Transact, for 1796, p. 186. Sir 

 John Herschel in the Observations at the Cape, pp. 350-352; 

 as also in Mrs. Somerville's excellent work, Connexion of the 

 Physical Sciences, 1846, p. 407. 



