327 



BOOK II. 



CHANGES IX THE INORGANIC WORLD NOW IN PROGRESS. 



CHAPTEE XV. 



AQUEOUS CAUSES. 



DIVISION OF THE SUBJECT INTO CHANGES OF THE ORGANIC AND INORGANIC 

 WORLD — INORGANIC CAUSES OF CHANGE DIVIDED INTO AQUEOUS AND IGNEOUS 



AQUEOUS CAUSES FIRST CONSIDERED — FALL OF RAIN RECENT RAIN-PRINTS 



IN MUD— EARTH-PYRAMIDS FORMED BY RAIN IN THE TYROL AND SWISS ALPS 



DWARF'S TOWER NEAR VIESCH DESTROYING AND TRANSPORTING POWER 



OF RUNNING WATER NEW1Y-FORMED VALLEYS IN GEORGIA SINUOSITIES OF 



RIVE RS— TWO STREAMS WHEN UNITED DO NOT OCCUPY A BED OF DOUBLE 

 SURFACE — 



- INUNDATIONS IN SCOTLAND FLOODS CAUSED BY LANDSLIPS IN 



THE WHITE MOUNTAINS— BURSTING OF A LAKE IN SWITZERLAND— DEVASTA- 

 TIONS CAUSED BY THE ANIO AT TIVOLI— EXCAVATIONS IN THE LAVAS OF ETNA 

 BY SICILIAN RIVERS— GORGE OF THE SIMETO— GRADUAL RECESSION OF THE 

 CATARACT OF NIAGARA. 



Geology was defined to be the science which investigates the 

 former changes that have taken place in the organic as well 

 as in the inorganic kingdoms of Nature. As vicissitudes in 



inic world are most apparent, and as on them many 

 llllv , uauiu ns in the animate creation must depend, they may 

 claim our first consideration. The great agents of change 

 in the inorganic world may be divided into two principal 

 classes, the aqueous and the igneous. To the aqueous belong 

 Rain, Rivers, Springs, Currents, and Tides ; to the igneous, 

 Volcanos, and Earthquakes. Both these classes are instru- 

 ments of degradation as well as of reproduction ; but they 

 may also be regarded as antagonist forces. For the aqueous 

 agents are incessantly labouring to reduce the inequalities 

 of the earth's surface to a level; while the igneous are 

 equally active in restoring the unevemiess of the external 





