174 
ELEMENTS OF GEOLOGY. 
CHAPTER XII. 
POST-PLIOCENE PEEIOD, CONTINUED.—GLACIAL CONDITIONS, 
CONCLUDED. 
Glaciation of Scandinavia and Russia.—Glaciation of Scotland.—Mammoth 
in Scotch Till.—Marine Shells in Scotch Glacial Drift.—Their Arctic Char¬ 
acter.—-Rarity of Organic Remains in Glacial Deposits.—Contorted Strata 
in Drift.—Glaciation of Wales, England, and Ireland.—Marine Shells of 
Moel Tryfaen.—Erratics near Chichester.—Glacial Formations of North 
America.—Many Species of Testacea and Quadrupeds survived the Glacial 
Cold.—Connection of the Predominance of Lakes with Glacial Action.— 
Action, of Ice in preventing the silting up of Lake-basins.—Absence of 
Lakes in the Caucasus.—Equatorial Lakes of Ahdca. 
Glaciation of Scandinavia and Russia.— In large tracts of 
Norway and Sweden, where there have been no glaciers in 
historical times, the signs of ice-action have been traced as 
high as 6000 feet above the level of the sea. These signs 
consist chiefly of polished and furrowed rock-surfaces, of 
moraines and erratic blocks. The direction of the erratics, 
like that of the furrows, has usually been conformable to the 
course of the principal valleys; but the lines of both some¬ 
times radiate outward in all directions from the highest 
land, in a manner which is only explicable by the hypothesis 
above alluded to of a general envelope of continental ice, 
like that of Greenland (p. 170). Some of the far-transported 
blocks have been carried from the central parts of Scandina¬ 
via towards the Polar regions ; others southward to Den¬ 
mark ; some south-westward, to the coast of Norfolk in Eng¬ 
land ; others south-eastward, to Germany, Poland, and Rus¬ 
sia. 
In the immediate neighborhood of Hpsala, in Sweden, I 
had observed, in 1834, a ridge of stratified sand and gravel, 
in the midst of which occurs a layer of marl, evidently form¬ 
ed originally at the bottom of the Baltic, by the slow growth 
of the mussel, cockle, and other marine shells of living spe¬ 
cies, intermixed with some proper to fresh water. The ma¬ 
rine shells are all of dwarfish size, like those now inhabiting 
the brackish waters of the Baltic; and the marl, in which 
many of them are imbedded, is now" raised more than 100 
feet above the level of the Gulf of Bothnia. Upon the top of 
this ridge repose several huge erratics, consisting of gneiss for 
the most part unrounded, from nine to sixteen feet in diame- 
