S5 o IN STARRY REALMS. 



surface, passing through the various stages of incandes- 

 cence, sank at length to a temperature comparatively 

 cool. Still the earth was swathed with a deep and dense 

 mantle of air, charged with an enormous load of watery 

 vapour ; but, as the temperature of the surface gradually 

 decreased, at length the watery vapours were condensed 

 and descended to form the oceans with which our earth is 

 so largely covered. At this point the functions of the 

 astronomer are at an end : he has traced in outline the 

 manufacture of the earth from the primeval nebula ; he 

 has accounted for its revolution round the sun, for its 

 rotation on its axis ; he has accounted for the shape of the 

 earth and for its internal heat. His work being done, he 

 now hands over the continuance of the history to the 

 biologist. 



The lifeless earth is the canvas on which has been drawn 

 the noblest picture that modern science has produced. 

 It is Darwin who has drawn this picture. He has shown 

 that the evolution of the lifeless earth from the nebula is 

 but the prelude to an organic evolution of still greater 

 interest and complexity. He has taken up the history of 

 the earth at the point where the astronomer left it, and he 

 has made discoveries which have influenced thought and 

 opinion more than any other discoveries that have been 

 made for centuries. We here encounter a very celebrated 

 difficulty. The theory of Darwin requires life to begin 

 with, but how did that life originate? I need hardly 

 remind you of the celebrated controversy which has taken 

 place on this subject. It has been contended that life can 

 never be produced except from life ; but just as stoutly 

 has the opposite view been maintained. Can it be pos- 



