632 CONCLUDING EEMAEKS. [Ch. XXXVIII 



Astronomy has been unable to establish the plurality of habitable 

 worlds throughout space^ however favourite a subject of conjecture and 

 speculation ; but geology, although it cannot prove that other planets 

 are peopled with appropriate races of living beings, has demonstrated 

 the truth of conclusions scarcely less wonderful, — the existence on our 

 own planet of so many habitable surfaces, or worlds as they have been 

 called, each distinct in time, and peopled with its peculiar races of 

 aquatic and terrestrial beings. 



The proofs now accumulated of the close analogy between extinct 

 and recent species are such as to leave no doubt on the mind that the 

 same harmony of parts and beauty of contrivance which we admire in 

 the living creation, has equally characterized the organic world at remote 

 periods. Thus as we increase our knowledge of the inexhaustible variety 

 displayed in living nature, and admire the infinite wisdom and power 

 which it displays, our admiration is multiplied by the reflection, that it 

 is only the last of a great series of pre-existing creations, of which we 

 cannot estimate the number or limit in times pastof 



* See Principles of GeoL, Book 3. 



f See tlie author's Anniv. Address to the GeoL Soc. 1837. Proceedings G. 8. 

 vol. ii. p. 620. 



