381 



which are of the same species as those found on the shells of the re- 

 cent strata in contact with the rocks, prove that the gneiss was long 

 submerged beneath the waters, and that the shells were not washed up 

 by an inroad of the sea upon the land. In the island of Orust, opposite 

 Uddevalla, I found similar appearances, and on other parts of the 

 western coast ; but on the eastern shores of Sweden or those bor- 

 dering the Baltic, both to the north and south of Stockholm, a 

 marked distinction is recognized. In the assemblage of fossil shells 

 which there occur in beds of upraised gravel, sand, and clay, the 

 testacea belong to recent species, yet riot to that assemblage which 

 inhabits the ocean, but to a confined number of mixed freshwater 

 and marine species characteristic of the brackish waters of the Baltic. 

 Such deposits rise near Stockholm to the height of 200 feet above 

 the sea, and show that the relative level of land and sea has greatly 

 changed, not only since the existing testacea were in being, but also 

 since the Baltic was divided off from the ocean as an inland sea 

 freshened by a superabundance of river water. 



It is well known that these parts of Sweden are densely strewed 

 over with huge erratic blocks, many of the largest of which oc- 

 cur in the highest part of ridges of sand and gravel, finely stratified 

 or made up of a continued series of thin layers of sand, loam, and 

 gravel. In one of these ridges, at Upsala, I found layers of marl, 

 containing perfect shells of recent species, such as live in the Baltic. 

 The ridge was about 100 feet high, and on the summit of it were 

 blocks of gneiss and granite, measuring from eight to ten feet in 

 length. I saw similar boulders but inferior in size overlying some 

 deposits of recent shells in Orust and near Uddevalla *. Hence it 

 is evident that the transportation of these rocky fragments into 

 their present position continued after the period when the modern 

 shelly formations of both the coasts of Sweden were accumulated. 



In addition to the facts enumerated in my paper on Sweden in the 

 Philosophical Transactions for 1835, in regard to the agency of ice- 

 islands, I may mention a fact observed by Dr. Beck on the coast of 

 Jutland. He has ascertained that on the breaking up of the fringe of 

 ice which encircles the coast there during winter, small islands of ice 

 float off and carry with them not only small gravel from the beach 

 but stones four feet in diameter firmly frozen into the solid mass. 

 These ice-floes are sometimes driven eastward into the Cattegat, and 

 have been known to stop up the narrow part of the passage of the Great 

 Belt, and to cause new reefs of rocks thus transported on which ves- 

 sels, and a few years ago a Danish man-of-war, have been stranded. 

 If such power can be exerted by ice-islands, only a few hun- 

 dred feet in diameter, in latitudes corresponding to those of En- 

 gland, we may be well prepared to find that islands several leagues 

 in circumference may remove blocks of the magnitude of small 

 houses. 



Capt. Bayfield, in commenting on the inferences which I had 

 drawn as to the transporting power of ice in the Baltic, communi- 



» Phil. Trans., 1835, p. 33. 



