OF THE COSMOS. VARIABLE STARS. 177 



of light in stars may possibly have on climatology in general, 

 on the history of the terrestrial atmosphere, i. e. on the 

 varying quantity of heat received in the course of ages by our 

 planet from solar radiation, and on the condition of organic 

 life, and its forms of development, in different latitudes. The 

 variable star, Mira Ceti, changes from the 2d to the llth 

 magnitude, and even to entire disappearance ; and we have 

 just seen that 77 Argus has increased from the 4th to the 

 1st magnitude, and even to the brightness of Canopus, and 

 almost to that of Sirius. If only a very small part of such 

 alterations of luminous intensity and radiant heat, either in 

 the ascending or descending scale, should have taken place 

 in our Sun (and why should it be different from other suns ?), 

 they would have produced more powerful and even more 

 fearful consequences to our planet, than are required for the 

 explanation of all geological relations and ancient telluric 

 revolutions. William Herschel and Laplace were the first 

 who called attention to these considerations. If I thus notice 

 them in this place, however, it is not because I would seek 

 exclusively in them for the solution of the great problem of 

 the alterations of temperature upon our globe. It may also 

 have been that the primitive high temperature of the planet 

 due to the manner of its formation and to its consolidation, 

 the radiation of heat through deep fissures or open clefts, and 

 veins not yet filled with metallic ores, more powerful elec- 

 tric currents, and a very different distribution of land and 

 sea, may, in the earlier ages of our planet, have rendered 

 the distribution of temperature independent of latitude, i. e. 

 of position relatively to the Sun. Cosmical contemplation 

 ought not to limit itself by too partial a view to astrognostic 

 relations only. 



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