MECHANICAL ACTION OF GLACIERS. 161 



are also found in the large moraines of which mention has 

 been made. 



Debris of moraines cover likewise great extents of low- 

 lyinglandsand valleys; and they there entail no small amount 

 of labour in clearing the ground for cultivation. To obtain 

 ground fit for cultivation 50 centimetres, or 20 inches, in 

 depth, it is often necessary to dig out and carry away 

 erratic stones which would have covered the whole area 

 to a depth of a metre, or 40 inches. 



Beds of clay and banks of shells of the glacial period are 

 often found spread over areas of great extent, especially 

 in districts open to deposits from Silurian regions of lime- 

 stone and argilaceous schists, which have been ground 

 down and worn away during the glacial period. Trans- 

 ported as moraine mud by the waters flowing from the 

 glaciers, they have formed beds under the surface of the 

 sea in these ancient times. In different places the lower 

 bed of clay is limestone or marly clay ; often it is filled with 

 diversely shaped lumps of hard marl, which sometimes 

 enclose fossils. This marly clay has made fertile the flat 

 country of Remerike and of Smaalehnene, the east part of 

 the valley of Chribtiania, Eker, the west flat part of Ring- 

 erike, Jasderen, and the flat country of Drontheim. The 

 marshy and peat lands of Listerland and of Ja^deren rest 

 on a bed of marine clay. For all of this information I am 

 indebted to the reports by Dr Broch and Principal Forbes ; 

 and this is also the case with what follows. It is only the 

 circumstance of rny having neglected to mark quotations 

 in MS. notes made years ago, which prevents me from 

 indicating such here. 



By the fragmentary shells found in cretaceous sand, the 

 succession of molluscs, both marine and those of fresh- 

 waters, may be traced. For our present purpose it is 

 enough to notice that by the remains of these the ground 

 has been enriched. 



In going up one of the great water-courses from the sea 

 towards its source we come first to a level where the 



M 



