Iceberg Theory. 109 



the rocks in a way similar to moving glaciers. But upon 

 such grounds they would sooner or later be stranded ; and if 

 they remained loose enough to move, they would, in their 

 gyratory movements, produce curved lines, and mark the 

 spots where they had been stranded with particular indica- 

 tions of their prolonged action. But nowhere upon arctic 

 ground do we find such indications. Everywhere the po- 

 lished and scratched surfaces ar» continuous in straight 

 juxta-position. 



Phenomena analogous to those produced by icebergs would 

 only be seen along the sea-shores ; and if the theory of drifted 

 icebergs were correct, we should have, all over those conti- 

 nents where erratic phenomena occur, indications of retreat- 

 ing shores as far as the erratic phenomena are found. But 

 there is no such thing to be observed over the whole extent 

 of the North American continent, nor over Northern Europe 

 and Asia, as far as the northern erratics extend. From the 

 arctics to the southernmost limit of the erratic distribution, 

 we find nowhere the indications of the action of the sea as 

 directly connected with the production of the erratic pheno- 

 mena. And wherever the marine deposits rest upon the 

 polished surfaces of ground and scratched rocks, they can be 

 shewn to be deposits formed since the grooving and polishing 

 of the rocks, in consequence of the subsidence of those tracts 

 of land upon which such deposits occur. 



Again, if we take for a moment into consideration the im- 

 mense extent of land covered by erratic phenomena, and view 

 them as produced by drifted icebergs, we must acknowledge 

 that the icebergs of the present period at least, are insufiicient 

 to account for them, as they are limited to a narrower zone. 

 And to bring icebergs in any way within the extent which 

 would answer for the extent of the distribution of erratics, 

 we must assume that the northern ice-fields, from which 

 these icebergs could be detached and float southwards, were 

 much larger at the time they produced such extensive pheno- 

 mena than they are now. That is to say, we must assume 

 an ice period ; and if we look into the circumstances, we shall 

 find that this ice period, to answer to the phenomena, should 

 be nothing less than an extensive cap of ice upon both poles. 



