135 EEA OF THE SUPERFICIAL FORMATIONS. COMMENCEMENT OF PRESENT SPECIES. We have now completed our survey of the series of stratified rocks, and traced in their fossils the progress of organic creation down to a time which seems not long antecedent to the appearance of man. There are, nevertheless, memorials of still another era or space of time which it is all but certain did also precede that event. The first that calls for notice is the phenomenon to which geologists have applied the term denuda tion. Great hitches and slips are detected in superficial strata,—such as, if left in their original state, must have caused considerable inequalities on the face of the country; yet all is found as smooth—the joinings are all as much reduced to a common level—as if some gigantic artificial force
