108 Iceberg Theory. 



hension that the heavy ocean-currents, the action of which 

 he sees everywhere, might have swept him away.* 



Now that these phenomena have been observed exten- 

 sively, we may derive also some instruction from the limits 

 of their geographical extent. Let us see, therefore, where 

 these polished, scratched, and furrowed rocks have been 

 observed. 



In the first place they occur everywhere in the north 

 within certain limits of the arctics, and through the colder 

 parts of the temperate zone. They occur also in the southern 

 hemisphere, within parallel limits, but in the plains of the 

 tropics, and even in the warmer parts of the temperate zone 

 we find no trace of these phenomena, and nevertheless the 

 action of currents could not be less there, and could not at 

 any time have been less there than in the colder climates. 

 It is true, similar phenomena occur in Central Europe, and 

 have been noticed in Central Asia, and even in the Andes of 

 South America, but these always in higher regions, at de- 

 finite levels above the surface of the sea, everywhere indi- 

 cating a connection between their extent and the colder 

 temperature of the places over which they are traced. 



More recently, a step towards the views I entertain of this 

 subject has been made by those geologists who would ascribe 

 them to the agency of icebergs. Here, as in my glacial 

 theory, ice is made the agent ; floating ice is supposed to 

 have ground and polished the surfaces of rocks, while I con- 

 sider them to have been acted upon by terrestrial glaciers. 

 To settle this difference we have a test which is as irre- 

 sistible as the other arguments already introduced. 



Let us investigate the mode of action, the mode of trans- 

 portation of icebergs, and let us examine whether this cause 

 is adequate to produce phenomena for which it is made to 

 account. As mentioned above, the polished surfaces are con- 

 tinuous over hills, and in depressions of the soil, and the 

 scratches which run over such undulating surfaces are never- 

 theless continuous in straight lines. If we imagine icebergs 

 moving upon shoals, no doubt they would scratch and polish 



* Berlin Academy, 1840. 



