268 GEOLOGICAL MEMOIRS. 



Pectens, may have some connection with the abundance of amber 

 and brown coal in these localities, the cause being that the western 

 part of the formation was deposited on the nearly level shores of a 

 sandy country, while the brown coal of the Cattegat was derived 

 from a district occupied by the old rocks, which formed the im- 

 mediate shores of a deep sea. 



The third system of the Brown coal formation is exhibited on 

 the islands of Mors and Fuur, in Liimfjord, and at several places 

 on the western shores of the fjord. The deposits of this part con- 

 sist of black clay and black unconsolidated sandstone, resting on 

 black limestone, these beds being overlaid by a very thick bed of 

 white infusorial siliceous earth, with subordinate layers of ferru- 

 ginous limestone, the whole being finally covered up by a yelloAv 

 sandstone and conglomerate. The stratification of the whole is 

 greatly disturbed. 



This formation is of freshwater origin, and contains insects, 

 fragments of freshwater fishes, and an immense multitude of a 

 small species of Spirorbis; but its relation to the marine beds of 

 western Jutland is evident in several places, strata of brown 

 coal, containing Cassidaria echinophora, appearing in the island of 

 Mors, and a black limestone, with Nucula glaberrima, in Thye. 

 Boulders are only found in the uppermost or sandy member of 

 this series, and are there very rare. 



The next great division of the boulder formation of Denmark I 

 have called " Boulder clay." It includes clays of yellow and blue 

 colour, and marls and sand, and throughout the whole, boulders 

 are distributed whose dimensions vary from the size of several 

 hundred cubic feet to that of a grain of sand. This formation has 

 been traced to the depth of several hundred feet, and the boulders 

 are distributed throughout the entire mass, their occurrence being 

 unquestionably not merely a surface phenomenon, but extending to 

 the deepest part of the series ; and the more common appearance of 

 the boulders at the surface is owing to the fact that the finer por- 

 tions have been washed away by a more recent denudation, which 

 however was not sufficiently powerful to remove the larger 

 blocks.* 



Of the series now under consideration, the yellow and blue clay 

 with boulders is very rarely stratified, but here and there a slaty 

 clay appears without boulders, and the sandy portions generally, 

 although by no means always, exhibit stratification. 



The irregularity of the interior of this deposit shows itself in 

 the external surface, — the whole forming a much intersected, hilly 

 district, without any regular chain being traceable, and the fertile 

 soil of the trough-like valleys is thickly covered with beech trees, 

 or the land is turned into corn-fields or used for pasture. This 

 formation is distributed here and there over most parts of Den- 

 mark, but covers entirely the southern part of the island of Seeland, 



* On the cliffs of Visborg in the island of Samsoe this alternation of finer 

 with coarser boulders is clearly seen repeated as many as four times. 



