172 THE RECENT. 



language, mental constitution, and religious sentiment of 

 the human race, will still contend for several creative 

 centres, must seek other corroboration of their hypothesis 

 than is yet afforded by the discoveries and indications of 

 geology. 



-As the pre-glacial passed gradually into the glacial, and 

 the glacial into the post-glacial period ; so the pre-human 

 passes insensibly into the pre-historic, and the pre-historic 

 into the historical ages. And even when the historical 

 arrives, the record of our own race is often less certain in 

 the hands of the historian than in those of the geologist. 

 Geology by no means ceases where history begins. Vast 

 physical changes have occurred since man first peopled the 

 globe.* Some regions have been rising above the waters of 

 the ocean, others have been sinking. Rivers have changed 

 their courses ; lakes and estuaries have been converted 

 into alluvial tracts ; and volcanoes have given birth to new 

 mountain masses. 



" There rolls the deep where grew the tree ; 

 Oh, Earth, what changes hast thou seen ! 

 There, where the long street roars, has been 

 The stillness of the central sea." 



Of such mutations, history is altogether silent ; and even 

 where she speaks, her utterance is frequently of less value 

 than her silence. The earth, however, pens and preserves 

 with fidelity her own record : geology becomes her inter- 

 preter. As in the physical world, so also in the vital, im- 

 portant mutations have been effected, even within historical 

 times. Many local removals of species and several general 



* For an able and lucid exposition of the recent changes to which the 

 earth has been subjected, the reader is referred to Sir Charles Lyell's 

 Principles of Geology a work which should be carefully studied by every 

 one who would lay a logical and solid foundation for his geological know- 

 ledge. 



