RECORDS LEFT BY RIVERS 



especially in flood-time. In any ordinary flood trees and 

 shrubs, and the smaller animals like mice and moles and 

 rabbits, are drowned by the flood. In greater floods 

 birds and even large animals are drowned, and their 

 remains are buried in the sediment. If they are quite 

 covered over they may perhaps be preserved, and their 

 bones may last for an indefinite period. If, further, the 

 mud deposit hardens, these remains may be preserved so 

 well and so long that they become the fossil records of 

 creatures which lived before man emerged to dwell in the 

 world and to become the arbiter of many of its destinies. 

 What we have said of rivers is true also of lakes. 

 Rivers pour into lakes, bringing with them, especially 

 in flood-time, enormous freights of gravel, sand, and mud, 

 and mingled with them the remains of vegetation and of 

 animal life. Hundreds of thousands of tons may be 

 swept down by one storm. To the Lake of Lucerne, for 

 example, the River Reuss, which comes down from the 

 St. Gothard, brings seven million cubic feet of sediment 

 every year with it. Since the time of the Romans the 

 Rhone has so filled up part of the Lake of Geneva that 

 the Roman harbour, Port Valais, is now nearly two miles 

 from the edge of the lake. The ground between it and 

 the Lake first became marsh. It is now farm land. 

 And though these accumulations are most marked where 

 the rivers drain into the lake, there are deposits always 

 taking place from the hills all round the lake. Thus 

 lake bottoms become most interesting and valuable 

 receptacles of the life that has for ages lived by or 

 near their shores. These deposits are in many ways 



56 



