6 MR. LYELL ON THE PROOFS OF A GRADUAL RISING OF 



SO that they afford a clear indication of a change in the relative level of that sea to the 

 amount of thirty feet since its waters were inhabited by the existing species of Testacea. 

 On inquiring whether any other examples had been observed of similar deposits of 

 shells, I was informed by Colonel Hallstrom that he had discovered them on the 

 farm of Orby, near Brankyrka, about three miles to the south of Stockholm. He 

 obligingly accompanied me to the spot, where I found strata of marl and sand fill- 

 ing the bottom of a valley situated in a broken tract of ground where the funda- 

 mental rock is gneiss. This tract of land intervenes between Lake Maeler and 

 the sea. 



The shells are very numerous, and are for the most part imbedded in a peaty soil 

 containing fragments of wood. The peat has perhaps been derived from sea-weed, 

 large accumulations of which I saw recently heaped up in a bay of the Baltic near 

 Solvitzborg, intermixed with similar species of shells. The identity of the shells of 

 Brankyrka with those of the neighbouring sea was even more complete than at 

 Solna ; for in addition to the species before enumerated, I found the Neritina Jiuvia- 

 tilis, a freshwater shell which lives in abundance in the brackish waters of the Baltic, 

 and which I saw covering the rocks in the saltish water at Graso, near Oregrund. 

 The Baltic variety is small, and usually black ; but both in the recent and fossil 

 individuals it sometimes exhibits its usual variety of colours. Some specimens also 

 of a land shell (Bulimus luhricus) occurred with the marine at Brankyrka. 



The height of these shells has been determined by Colonel Hallstrom to be seventy 

 Swedish feet above the Baltic ; so that they indicate a fall of the waters, or rather a 

 rise of the land, to that amount, since the neighbouring gulf was inhabited by this 

 assemblage of Testacea. But the most remarkable spot where these Baltic shells 

 occur in a fossil state is still further to the south, at Sodertelje (see the Map, Plate I.), 

 about sixteen miles south-west of Stockholm, where they are found elevated more than 

 ninety feet above the sea. At Sodertelje a canal was cut in 1819 across a barrier 

 of sand, gravel, and clay, which separated Lake Maeler from a long narrow inlet or 

 frith of the Baltic. The canal is, in fact, carried through the bottom of one of those 

 valleys so common in this district, of which the sides consist of rocks of gneiss, and 

 the bottom of the same covered by more recent deposits. The accompanying trans- 

 verse section (fig. 3.) will explain this geological structure. 



Fig. 3. 



Section across the valley of Sddertelje, showing the position of the new deposits in relation to the gneiss. 



The boundary hills of bare rock rise to the height of two hundred feet, the newer for- 

 ination being in some places about one hundred feet high, while on others, as on the 

 site of the Lake Maren, there are hollows which sink beneath the level of the sea. 



