100 THE PRIMARY PERIODS. 



past ! Like the prehistoric relics of the shell-mounds, the 

 lake-dwellings, the caves, and the river-gravels, they may 

 lead to no very definite or connected view of the aspects 

 and history of the periods to which they relate; but to 

 science they are invaluable as proving what has been there, 

 and as indicating the design and method of creation. 

 Where everything is so obscure the faintest glimmer be- 

 comes an unspeakable boon a certainty of itself where- 

 from to predicate, and the strongest incentive to further 

 investigation. 



