PLAINS OF THE ELBE, ODEE, AND VISTULA. 



300 



of shells and animals discovered in the drift appear to prove that the climate 

 was colder when these erratics were being dispersed than it is now. Bones of 

 mammoths and rhinoceroses have likewise been found. 



Lakes and Peat Bogs. 



When the sea retired from the land numerous cavities remained filled with 

 water. Many of these have now become filled up with alluvial soil, but owing 

 to the gentle slope of the plain, deposition proceeds at so slow a rate that the lakes 

 of Northern Germany, large and small, can be counted by the hundred. All 

 these lakes are now filled with fresh water, with the exception of one in the 

 vicinity of Eisleben, which is evidently fed from brine springs. The whole of 

 the Harz, an ancient island of the ocean, is surrounded by saliferous strata. At 

 Speremberg, a village near Jiiterbogk, the borer first struck salt at a depth of 



Fig. 172. — The Lake District of Masuria. 

 Scale 1 : 2.100,000. 



,ia*' E.oi Part's 



Yb Miles. 



290 feet, and then passed through a bed of it 3,880 feet in thickness. The sea 

 which deposited this salt must have been at least 3,800 fathoms in depth. 'J he 

 boring at Speremberg is the deepest in the world. It furnished interesting 

 information on the temperature of the earth. The temperature ceased to increase 

 after a depth of 5,316 feet had been attained, and amounted to 12" Fahr. at 

 the bottom of the boring. The salt-mines of Stassfurt, on the Saale, are equally 

 curious. 



Lakes abound on the northern slope of the heights of Mecklenburg. Some of 

 them occupy cavities in the rocks, and are said to be more than 600 feet in 

 depth. As to the coast lakes of Mecklenburg, they are gulfs or fiords, like those 

 of Norway, but in a state of transition. Some of the lakes shed their waters into 

 rivers flowing in opposite directions. 



The rivulets which flow southwards from the hills of Pomerania expand into 

 lakes or ponds. To the east of the Vistula, in the country of the Masures, the 



