FORCHHAMMEB ON THE BOULDER FORMATION. 271 



gularly lying Brown coal series of Western Jutland is seldom 

 covered with the boulder clay, and then only at intervals. Now, 

 since also in the only place in the western system where we know 

 of the existence of greatly inclined strata of the Brown coal 

 series, namely, on the island of Sylt, it is also covered with a thick 

 bed of boulder clay : it appears clearly made out that the cause 

 of the deposit of this bed was identical with that which has 

 disturbed the strata of the Brown coal series. With reference to 

 this point it is also not unimportant to notice that the boulder clay 

 of Sylt contains so many fragments of true lava, that the in- 

 habitants of the island have remarked it, and designated it by the 

 name of Bimmstein (pumice). Carrying out this view, the presence 

 of calcareous and schistose fragments of the old rocks, in several 

 spots where they are so common that attempts have been made to 

 reach the supposed subjacent rocks themselves, is an important 

 fact, since it would seem to point to a possible continuation of the 

 silurian rocks, which we are enabled to trace from the lake of 

 Ladoga as far as Bornholm. 



The last member of the boulder formation consists of sand and 

 rolled fragments, and I have called it the " boulder-sand-formation." 

 Sometimes the sand is argillaceous, but I have not observed true 

 argillaceous bands in the formation itself, although it is sometimes 

 overlaid by a brown clay without calcareous matter which formed 

 the last precipitate, if I may so say, after the greatly disturbed 

 ocean had at length become calm. This formation (the boulder- 

 sand) is always stratified, but the strata are generally highly in- 

 clined, much curved, sharply broken off, and in a word resemble 

 those strata which the greatly disturbed waves now deposit on 

 our coast. The surface of the country where this formation pre- 

 vails is much varied, and consists sometimes of complete chains of 

 hilly ground greatly inclined on both sides, and perfectly resembling 

 in that respect the Swedish Aosar, but analogous also to the so- 

 called Bevler on the west coast of Jutland, where parallel banks 

 of sand and stones are separated from one another by the sea at 

 high water. Another form in which this formation presents 

 itself (seen in North Seeland and North Jutland), is that of a hilly 

 sandy district, without the hills having any distinct direction ; and 

 a third form exhibits hemispherical hills, some a hundred feet high 

 and near together, the valleys being merely the spaces between 

 several of these segments of spheres. This latter form is seen 

 on the Cape, at the Cattegat, and in the island of Samsoe, and a 

 fourth form is observable on the peninsula, where a thin covering 

 of this part of the series rests on the level expanse of the Brown 

 coal formation. 



Large boulders are not found in this formation ; the solid content 

 of those that occur being seldom so great as two cubic feet, while 

 all of them are completely rounded, and they are sometimes so nu- 

 merous that the sand only fills up the interstices between them ; 

 while on the other hand, the sand occasionally forms so large a 

 proportion of the whole mass, that there are only a few boulders to 



