372 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



The fall of some of these blocks, together with the accompanying 

 mass of gravel and sand, would, in fact, cover up and destroy one 

 or more of these cottages ; and if the tract were abandoned for 



Fig. 15. 



Road. 



centuries by human beings, future geologists might reasonably be led 

 to contend, if judging from these evidences alon^, that from the ves- 

 tiges of subjacent buildings, the angular blocks and even the rounded 

 gravel had been ti'ansported over this continent subsequently to its 

 habitation by man. 



In approaching Hedemora, or in ascending to that town, which 

 lies about 150 or 200 feet above the river Dal Elf (a stream which 

 there, as in many parts of its course, resembles a quiet lake), the 

 whole tract is one of undulating hilly sands exactly similar to those 

 south of Christianstad in Scania, and equally resembling the bottoms 

 of a former sea, the summits in both cases being capped with angu- 

 lar blocks of crystalline granitic and gneissose rocks. In approach- 

 ing Sater, these sands constituting linear osar, which are here and 

 there united by cross bands or bars, are covered by worn boulders 

 and gravel ; and further on the osar are entirely composed of water- 

 worn boulders, as coarse as those forming the os of Bronkeberg 

 near Stockholm. Osar like these, which separate the water-courses 

 and lakes, are, as M. Brongniart has before remarked, natural 

 chaussees or elevated mounds on which all the roads run. Again, 

 the ravines at Sater, in which the water-course in a deep dell bounds 

 over gneissose rocks, the river banks on either side (as indeed in 

 numberless places along the Dal Elf) consist of mounds of finely 

 laminated sandy loam, the surface of the plateau alone being occu- 

 pied by large and angular blocks, which are still found in the nar- 

 row valleys or ravines, except when their incoherent sides have 

 given way within the modern period. In this case, the superjacent 

 blocks have been precipitated into the chasm below, and have car- 

 ried with them gravel or clay, according as the nature of the origi- 

 nal submarine materials or drift may determine. 



It is however essential to remark, that although upon the whole 

 the osar may be viewed as long narrow banks, such in fact as they 

 were described by M. Brongniart, there are very numerous excep- 

 tions. The prevalent linear or north and south direction, and the 

 shape of these masses, have necessarily been determined by the 

 chief physical features of Sweden, which consist of frequent alter- 

 nations of ridges of crystalline rocks and longitudinal depressions, 

 the latter being either filled with water or occupied by the gravelly 



