INTRODUCTION. 5 



reach through geological time are represented in order by the 

 rocks that extend from the lowest to the uppermost of the 

 series. 



8. If, now, the great beds of rock, instead of lying in even hori- 

 zontal layers, are much folded up, or lie inclined at various angles, 

 or are broken and dislocated through hundreds or thousands 

 of feet in depth, or are uplifted into mountain-elevations, they 

 bear record of still other events in the great history ; and should 

 the geologist, by careful study, learn how the great disturbance or 

 fracture was produced, or succeed in locating its time of occur- 

 rence among the epochs registered in the rocks, he would have 

 interpreted the record, and added not only a fact to the history, 

 but also its full explanation. The history is, hence, a history of 

 the upturnings of the earth's crust, as well as of its more quiet 

 rock-making. 



If, in addition, a fossil shell, or coral, or bone, or leaf, is found in 

 one of the beds, it is a relic of some species that lived when that 

 rock was forming : it belongs to that epoch in the world repre- 

 sented by the particular rock containing it, and tells of the life 

 of that epoch ; and if numbers of such organic remains occur 

 together, they enable us to people the seas or land, to our imagi- 

 nation, with the very life that belonged to the ancient epoch. 



Moreover, as such fossils are common in a large number of the 

 strata, from the lowest containing signs of life to the top, — that is, 

 from the oldest beds to the most recent, — by studying out the 

 characters of these remains in each, we are enabled to restore, to 

 our minds, to some extent, the population of all the epochs as 

 they follow one another in the long series. The strata are thus 

 not simply records of moving seas, sands, clays, and pebbles, and 

 disturbed or uplifted strata, but also of the living beings that 

 have in succession occupied the land or waters. The history is a 

 history of the life of the globe, as well as of its rock-formations ; 

 and the life-history is the great topic of Geology : • it adds tenfold 

 interest to the other records of the dead rocks. 



These examples are sufficient to explain the basis and general 

 bearing of geological history. 



The method of interpreting the records rests upon the simple principle that rocks 

 were made as they are now made, and that life lived in olden time as it now lives; 

 and, further, the mind is forced into receiving the conclusions arrived at by its own 

 laws of action. 



For example, we go to the sea-shore, and observe the sands thrown up by the 

 waves ; note how the wash of the waves brings in layer upon layer, though with 

 many irregularities ; how the progressing waters raise ripples OA r er the surface, 

 which the next wave buries beneath other sands; how such sand-beds gradually 



