INTRODUCTION. O 



to the history, but a] so 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 represented 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 imagination, with the very life that be- 

 longed 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 char- 

 acters 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 lifo 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 bear- 

 ing of geological history. 



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

 were made as they are now made, ami 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 irregu- 

 larities; how the progressing waters raise ripples over the surface, which the next wave 

 buries beneath other sands; how such sand-beds gradually increase in extent; how 

 they are often continued out scores of miles beneath the sea, as the bottom of the shal- 

 low shore-waters; and that these submerged beds are formed through constant deposi- 

 tions from the ever moving waters. Then we go among the hard rocks, and find strata 

 made of sand in irregular layers, much like those of the beach ; and on opening some 

 of the layers we discover ripple-marks covering the surface, as distinct and regular as 

 if just made by the waves; or, in another place, we find the strata made up of regular 

 layers of sand and clay alternating, such as form from the gradual settling of the 

 muddy material emptied into the ocean by rivers, — or, in another place, layers of 

 Tounded, water-worn pebbles, such as occur beneath rapidly-moving waters, whether of 

 waves or rivers. We remark that these hard rocks differ from the loose sand, clay, or 

 pebbly deposits simply in being consolidated into a rock. Then, in other places, we 

 discover these sand-deposits in all states of consolidation, from the soft, movable sand, 

 through a half-compacted condition, to the gritty sandstone; and, further, we discover, 

 perhaps, the very means of this consolidation, and see it in its progress, making rock 

 ■out of sand or clay. By such steps as these, the mind is borne along irresistibly to 

 the conclusion that rocks were slowly made through common-place operations. 



