406 Life and Immortality. 



ancient streams. But if the beds contain the remains of 

 mollusks, minute crustaceans or fish, such as are found 

 to-day in lakes, then we conclude that they are lacustrine, 

 and were deposited beneath the waters of former lakes. 

 And, lastly, if the remains of animals such as now people 

 the oceans are to be met with in the beds, then we know 

 that they are marine in origin, and that they are fragments 

 of an old sea-bottom. On the whole, the conditions under 

 which a bed was deposited, whether in a shallow sea, in the 

 immediate vicinity of a coast-line, or in deep water, can 

 often be determined with considerable accuracy from the 

 nature of the relics of the organisms which they contain. 

 But we have thus far been dealing with the remains of 

 aquatic animals. When, however, we consider the remains of 

 aerial and terrestrial animals, or of plants, the determination 

 of the conditions of deposition is not made out with such 

 an absolute certainty. Remains of land-animals would, of 

 course, occur in sub-aerial deposits, that is, in beds, like 

 blown sand, accumulated upon the land, but the most of 

 such remains of such animals are found in deposits which 

 have been laid down in water, and hence their present 

 position is due to the fact that their former owners were 

 either drowned in rivers or lakes, or borne out to sea by 

 water-channels. Animals possessed of the power of flight 

 might also similarly find their way into aqueous deposits, 

 but, when it is remembered that many birds and mammals 

 habitually spent a great part of their time in the water, it 

 is not to be wondered at that they should present themselves 

 as fossils in sedimentary rocks. Even plants, such as have 

 undoubtedly grown upon land, do not prove that the bed 

 in which they are found was formed on land, for many of 

 their remains are extraneous to the bed in which they now 

 occur, having reached their present site by falling into lakes 

 or rivers, or by being carried out to sea by floods or gales of 

 winds. Still, there are many cases which obviously show 

 that plants have grown on the very spot where we now find 



