4 AQUEOUS EOCKS. [Cn. 1. 



pebbles composed of flint, limestone, granite, or otber rocks, resembling 

 tbe shingles of a sea-beach or the gravel in a toirent's bed. Such layer? 

 of pebbles frequently alternate with others formed of sand or fine sedi • 

 ment, just as we may see in the channel of a river descending from hills 

 bordering a coast, where the current sweeps down at one season coarse 

 sand and gravel, while at another, when the waters are low and less rapid, 

 fine mud and sand alone are carried seaward.* 



If a stratified arrangement, and the rounded form of pebbles, are alone 

 suflScient to lead us to the conclusion that certain rocks originated under 

 water, this opinion is farther confirmed by the distinct and independent 

 evidence of fossils, so abundantly included in the earth's crust. By a 

 fossil is meant any body, or the traces of the existence of any body, 

 whether animal or vegetable, which has been buried in the earth by 

 natural causes. Now the remains of animals, especially of aquatic species, 

 are found almost everywhere imbedded in stratified rocks, and sometimes, 

 in the case of limestone, they are in such abundance as to constitute the 

 entire mass of the rock itself. Shells and corals are the most frequent, 

 and with them are often associated the bones and teeth of fishes, frag- 

 ments of wood, impressions of leaves, and other organic substances. Fossil 

 shells, of forms such as now abound in the sea, are met with far inland, 

 both near the surface, and at great depths below it. They occur at all 

 heights above the level of the ocean, having been observed at elevations 

 of more than 8000 feet in the Pyrenees, 10,000 in the Alps, 13,000 in 

 the Andes, and above 18,000 feet in the Himalaya.f 



These shells belong mostly to marine testacea, but in some places 

 exclusively to forms characteristic of lakes and rivers. Hence it is con- 

 cluded that some ancient strata were deposited at the bottom of the sea, 

 and others in lakes and estuaries. 



When geology was first cultivated, it was a general belief, that these 

 marine shells and other fossils were the effects and proofs of the deluge 

 of Noah ; but all who have carefully investigated the phenomena have 

 long rejected this doctrine. A transient flood might be supposed to leave 

 behind it, here and there upon the surface, scattered heaps of mud, sand, 

 and shingle, with shells confusedly intermixed ; but the strata containing 

 fossils are not superficial deposits, and do not simply cover the earth, but 

 constitute the entire mass of mountains. Nor are the fossils mingled 

 without reference to the original habits and natures of the creatures of 

 which they are the memorials ; those, for example, being found associated 

 together which lived in deep or in shallow water, near the shore or far 

 ft'om it, in brackish or in salt water. 



It has, moreover, been a favorite notion of some modern writers, who 

 were aware that fossil bodies could not all be referred to the deluge, 

 that they, and the strata in which they are entombed, might have been 

 deposited in the bed of the ocean during the period which intervened 



» See p. 18, fig. 1. 



I Capt. R. J. Strachey found oolitic fossils 18,400 feet high ia the Himalaya 



