4 A Pei^od in the History of our Planet, 



atlmiration of their sublimity, never dream, that what excites 

 their astonishment, is but the ruins of departed greatness. 



It is to the Glaciers, and the parent of that gigantic family 

 —the Glacial period, that I wish to draw the attention of my 

 readers. 



Through the inquiries of Geology, the conviction has be- 

 come universal, that our earth has not always existed in the 

 same form that it does at present ; that the inequalities of its 

 dry land, and the extent of its waters, once presented to the 

 eye a totally different appearance from what they do at pre- 

 sent ; that it was only by degrees, and by means of mighty re- 

 volutions, the influence of which elevated entire districts and 

 mountain-chains, and depressed others, that the firm crust of 

 the globe received its present form. These revolutions, to in- 

 quire into the results of which, in particular cases, forms one 

 of the great problems of geological inquiry, are the pillars 

 upon which the history of our earth is founded, the march- 

 stones which separate the sections of their periods of develop- 

 ment, and determine their different ages, — relatively only, no 

 doubt, for the determination, even approximatively, of the ab- 

 solute length of any such epoch, is still an unsolved problem. 

 We know, that the chalk is more ancient than the tertiary 

 formations, more recent than the Jura series : this we know, 

 with perfect distinctness ; but how long the epoch of the chalk 

 lasted, what period of time elapsed during its deposition, this 

 we do not know, nor have we at the present time any data for 

 determining. May we soon receive such by the industry of 

 our geologists ! 



A peculiar creation animated the earth during each sepa- 

 rate period that elapsed between one revolution and another ; 

 each period had its own creation, its particular type of organic 

 existence, and, as in the history of mankind, each great epoch 

 of culture receives a particular stamp, by a particular direc- 

 tion of the mind, peculiar to the epoch, so the totality of living 

 beings which existed upon the earth at a certain geological 

 period, and the remainsof which we find entombed in its entrails, 

 impresses upon this period a stamp which cannot be mistaken. 



Our present geology rests almost solely upon an acquaintance 



