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182 



GEOLOuV. 



[Sect. VI. 



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eir size, from p-^-'iial though rude measurements, should 



be given. 



Both in the north and south a peculiar formation called 

 '' till '' has boon found connected with erratic boulders ; 

 it consists generally of mud, containing angular and 

 rounded stones of all sizes up to the largest boulders, 

 mingled in utter confusion, and generally without any 

 stratification. Such deposits should be examined. Some- 

 times when they are stratified, the upper beds have been 



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found violeniiv contorted, whilst the lower ones are un- 

 disturbed, showing that the violence has not procc^^J^d 

 from below, as in ordinary geological cases. Sir C. Lyell 



has suggested that this effect has been produced by the 

 stranding of great icebergs. 



As far as our present knowledge goes, the abovo enu- 



merated phenomena — such a.^ scored, mamillated, and 

 pollahed rocks, moraines, erratic boulders, and beds of 

 ^ Lough occurring in latitudes where glaciers do not 

 now occur, w^here the sea is never frozen, and where 

 icebergs are never drifted, yet have not been observed in 





5 



dther hemisphere higher than about latitude 40^, Hence 

 on whatever coast ancient ice-action might be discovered, 

 the limit of latitude towards the tropics at which it ceases 



ought to be carefully investierated. Observations are 



much waritcd on the west coa-ist of N. America and the 

 east coast of Asia ; and again in New Zea^land and other 

 islands of the Southern Ocean. The period of the ice 

 action is pretty ,. Jl ascertained in Europe and North 

 America, and a very great service would be rendered to 

 geology if the same point could be clearly made out in 



the southern hemisphere ; for it might greatly influence our 



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