1846.] MURCHISON ON THE SCANDINAVIAN DRIFT. 359 



too easily affected by the atmosphere to have retained the outline 

 impressed upon it by the great mechanical forces which have swept 

 over this low tract and left so many of their traces upon it. 



Island of Gothland. 



Intending on a future occasion to give an account of the geolo- 

 gical structure of Gothland, I shall now only mention that the island 

 is from one end to the other * a mass of coralline and shelly lime- 

 stone, with some shale and limestone of most unequivocal Upper 

 Silurian age. Its surface, which is nowhere more than 200 feet 

 above the sea level, is covered with coarse northern gravel and 

 boulders, and overlying these are occasionally seen large erratic 

 blocks, the whole of this material being derived from the north, or 

 from points east and west of that direction. Notwithstanding this 

 accumulation of transported matter, the limestone is not only seen 

 in the coast cliffs, but in numerous ridges and points, where it rises 

 through the drift to the surface ; but in no place does it exhibit 

 proof of having been specially affected by powerful erosion so much 

 as on the north-eastern face of the island near Slite, where the lime- 

 stone of the rocks of Lanna has been probably worn by the power- 

 ful action of water into those grotesque forms of which Linnaeus 

 has left rude sketches in his description of Gothland. That these 

 currents have acted from N.E. to S.W. in the northern part of Goth- 

 land is, indeed, proved, not only by the detritus having been swept 

 in that direction, great quantities of it having been accumulated to 

 the south of Wisby (where it is both lodged on the surface of the rocks 

 and has been precipitated over the lofty cliffs, to form at their base 

 the bottom of the actual sea), but also by exhibiting in many places 

 where the gravel has been cleared away from the surface of the sub- 

 jacent rock, decisive marks of having grooved and striated the lime- 

 stone on which it rested. This is particularly well seen to the south 

 of Wisby, where gravel pits have been opened to procure the hard 

 granite and porphyry pebbles for the use of the roads. The surface 

 of the limestone thus exposed presents parallel grooves or flutings 

 from one to three inches wide at intervals of from six to nine 

 inches from each other, the whole of the rock having been smoothed 

 down by powerful friction, and marked by innumerable scratches, 

 which, deviating slightly from the absolute parallelism of the larger 

 grooves, yet preserve the same general direction. These markings 

 on the Upper Silurian limestone, which would have been long ago ef- 

 faced from this comparatively soft rock if it had been exposed to the 

 weather, do, I venture to say, so perfectly resemble the flutings and 

 striae produced in the Alps by the actual movement of glaciers, that 

 neither M. Agassiz nor any one of his supporters could detect a 

 difference. Yet where is the glacialist who will contend that terres- 

 trial glaciers passing over the Baltic Sea can have traversed this low 



* The length of the island is about eighty-four English miles. 



