338 SKETCHES OF CREATION 



CHAPTER XXXI. 



THE TOOTH OF TIME. 



A FEW words about the disintegration of the rocks 

 -*"*- As the vital force employs itself in the demolition ot 

 the organic structures and the simultaneous repair of all 

 the wastages, so the gigantic energies of geology have 

 busied themselves in one age or place in demolishing the 

 rocky fabrics consolidated with incredible labor in another 

 age or place. The grain of sand upon the rivulet's border 

 may have been incorporated successively into a dozen dif- 

 ferent formations, each in turn disintegrated to be in- 

 wrought in the rocky sheets of the next succeeding age. 



Has the reader ever inquired whence came the materials 

 for twenty-five miles of sedimentary strata ? It is a ques- 

 tion which geology is compelled to answer. The first and 

 lowest great system of strata — the Laurentian — is in Can- 

 ada thirty or forty thousand feet thick. This system is 

 supposed to embrace nearly the entire globe, passing be- 

 neath the Paleozoic, Mesozoic, and Cenozoic strata, and ex- 

 tending, probably with greatly diminished thickness, under 

 the beds of the existing oceans. It must have been accu- 

 mulated while yet the primeval sea was wellnigh univer- 

 sal. This is the prevalent opinion. It is perfectly plain, 

 however, that these vast beds of sediment must have had 

 an origin in pre-existing rocks lying within reach of the 

 denuding agencies of the time. How enormous a bulk of 

 solid rocks was ground to powder to furnish material for 

 these Laurentian strata may be imagined when the reader 

 is reminded that the mean elevation of North America is 



