4o6 NINETEENTH CENTURY. pt. in. 



as Hutton had been before him (see p. 219), that we can 

 only learn the past history of the earth by observing the 

 causes now at work. 



What Hutton had suggested Lyell worked out. He col- 

 lected with great care all that is known of changes going on 

 now all over the world, and the causes which produce them. 

 Among these were — 



istly. The fall of rain, and how it wears away the earth 

 and carries it off in little rills to the river. 



2ndly. The amount of mud carried by mighty streams, 

 such as the Ganges, the Nile, and the Mississippi, and laid 

 down in the sea at their mouths. 



3rdly. The amount of lime, iron, and other minerals 

 brought up by springs from the inside of the earth, and 

 thrown down on the surface. 



4thly. The tides and currents of the sea, and how they 

 wash up fresh land on some coasts and eat away the land 

 on others. 



5thly. The growth of corals in the sea, and how remains 

 of their skeletons become cemented into limestone. 



6thly. The volcanoes which are throwing out lava, and 

 how much they have thrown out in historical times. 



ythly. The different earthquakes which man has wit- 

 nessed, how they have broken and dislocated the land, 

 raising it in some places, as in New Zealand, and causing 

 it to sink in others, as at New Madrid, in America. 



8thly. The way in which plants and animals are buried 

 in the mud of lakes, or at the mouths of rivers, or in peat and 

 sand. 



All these, and many other changes which are taking 

 place all over the world in the present day, Lyell studied 

 with great accuracy, and then began a book to show that 



