18 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 8, 



Lower Silurian strata (viz. sandstone, alum slate (largely worked) 

 and Orthoceratite limestone) which has been pointed out at Kin- 

 nekulle and many other places on the mainland of Sweden. 



^ni?.?.Bii --r/^. Upper Silurian Rochs of Gothland. 



A wide channel of the sea separates Oland from Gothland. The 

 latter island, having a length of upwards of eighty English miles 

 and an average breadth of twenty to thirty miles, differs from the 

 former in being chiefly composed of shale and coralline limestone, 

 with some peculiar sandy and oolitic rocks towards its southern end ; 

 whilst all its strata contain fossils of Upper Silurian age. This 

 general inference was indeed long ago drawn from the description 

 of its fossils, and I was enabled, w^hen the ' Silurian System ' was pub- 

 lished, to identify the chief limestones of Gothland with the well- 

 known British types of Dudley and Wenlock. Independently of 

 a wish to collect many of these fossils on the spot and to determine 

 the nature of the drift and the surface-phsenomena of its rocks (as 

 described in a former memoir), I had a special interest in visiting 

 Gothland, in order to satisfy myself if the view suggested in the 

 second chapter of the work on Russia was correct ; viz. whether the 

 southern portion of the island was of more recent age than its main 

 mass, and could be paralleled with the Ludlow formation of England. 



Rising in no part to heights exceeding 250 to 300 feet above the 

 sea, Gothland, though well-watered, contains no stream of any note. 

 Extensively covered with northern drift, its depressions are occupied 

 by morasses, woodlands and lakes^ but its structure is nevertheless 

 well-exposed in numerous bold coast-cliffs. The great mass of the 

 island is a coralline limestone, so slightly deviating from horizontality, 

 that it is only by following the strata from N.N.W. to S.S.E. through- 

 out the whole length of the island, that any attempt at subdivision 

 can be made in them. 



On the west and north-west, or to the north and south of the chief 

 town, Wisby, a light grey coralline limestone is everywhere at the 

 surface, and in the sea-ward cliffs is seen to repose on dark grey 

 shale with nodules of earthy limestone. This succession occurs 

 at numerous points along the northern and north-western coast, 

 whether at Cappelhamn and Lummelund to the north, or at Hog 

 Klint to the south of Wisby. Thus at Nygard's jog (paper-i 

 mill), near Lummelund, the shale beneath the limestone is beauti- 

 fully exposed at a cascade, where the waters gathered from the in- 

 terior of the island and the adjacent lakes and marshes of Martebo, 

 and passing through subterranean courses in the limestone, gush out 

 in a fine broad torrent from the face of the abrupt cliff (brutt-klint), 

 and fall over the nodular shale, about fifty or sixty feet above the sek. 

 The slight undulation of the northern limestone is proved by the re- 

 appearance of the rock at intervals in the interior, from beneath the 

 incumbent mass of northern detritus, and by its forming the cliffs at 

 Slite and other places on the eastern as well as on the western coast, 

 in the parallel of Wisby. The numerous gates, churches and mo- 



