182 COSMOS. 



ation of its light-process, may account for far greater and 

 more fearful results for our own planet than any required foi 

 the explanation of aL geognostic relations and ancient telluric 

 revolutions. William Ilerschel and Laplace were the first 

 to agitate these views. If I have dwelt upon them some- 

 what 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 formation, and the solidification of con- 

 glomeratmg matter ; the radiation of heat from the deeper 

 strata of the earth through open fissures and through unfilled 

 veins ; the greater power of electric currents ; a very difier- 

 ent distribution of sea and land, may also, in the earliest 

 epochs of the earth's existence, have rendered the difiusion 

 of heat independent of latitude ; that is to say, of position 

 relatively to a central body. Cosmical considerations must 

 not be limited merely to astrognostic relations. 



V. 



PROPER MOTION OF THE FIXED STARS. — PROBLEMATICAL EXIST 

 ENCE OF DARK COSMICAL BODIES.— PARALLAX.— MEASURED DIS- 

 TANCES OF SOME OF THE FIXED STARS.— DOUBTS AS TO THE AS- 

 SUMPTION OF A CENTRAL BODY FOR THE WHOLE SIDEREAL HEAV 



ENS. 



The heaven of the fixed stars, in contradiction to its very 

 name, exhibits not only changes in the intensity of light, but 

 also further variation from the perpetual motion of the indi- 

 vidual stars. Allusion has already been made to the fact 

 that, without disturbing the equilibrium of the star-systems, 

 no fixed point is to be found in the whole heavens, and that 

 of all the bright stars observed by the earliest of the Greek 

 astronomers, not one has kept its place unchanged. In the 

 case of Arcturus, of jtz Cassiopeia?, and of a double star in Cyg- 

 nus, this change of position has, by the accumulation of their 

 mnual proper motion during 2000 years, amiounted respect- 

 ively to 2|-, 3^, and 6 moon's diameters. In the course of 

 3000 years about tAventy fixed stars will have changed their 

 pla3es by 1° and upward. =^ Since the proper motions of the 

 fixed stars rise from 2V "^^^ ^^ ^ second to 7"7 seconds (and 



* Encke, Betraclitiingen fiber die Anordanng des Stern- syst 2ms, s. 12 

 Vide svprj, I). 27. Miidler, Astr., s. 445. 



