INTERGLACIAL EPOCHS. 283 



deposits of Saxony is the commingling, in certain of the beds, 

 of stones which have come partly from the north and partly 

 from the south. This curious fact has been noticed by many 

 observers — by Cotta, Beyrich, Girard, Lasard, Orth, Credner, 

 Dathe, Penck, and Jentzsch. The Leipzig gravels, in which 

 chalk-flints derived from the north are common, are yet full of 

 stones which could only have come from the hilly districts to 

 the south ; and according to Dathe, south materials predominate 

 in the district between Dobeln and Dahlen close to the Prusso- 

 Saxon boundary. Southern stones also appear still farther east, 

 at Grossenkain, and in the country north of Dresden, between 

 Eadeberg and Kamenz. In this latter district the majority of 

 the stones are local or from the north, but among these an 

 occasional truant from the south may be detected. Such stones 

 of southern origin are restricted as a rule to the gravels (No. 2 

 of the preceding table) ; but now and again specimens are 

 found in boulder-clay. The origin of these phenomena is thus 

 explained by Penck. The lower sand with northern materials 

 pertains to the first glacial epoch at the climax of which the 

 northern mer de glace approached the base of the Harz and Erz 

 mountains, and covered Saxony with a sheet of boulder-clay. 

 Then came a change of climate when the ice-sheet melted away, 

 and when rivers and streams flowing north from the Saxon 

 highlands denuded and re-arranged the lower boulder-clay, and 

 commingled its stones and boulders with gravel and shingle 

 derived from the south. This was the first interglacial epoch. 

 After some time a second glacial epoch ensued, when a 

 northern ice-sheet again advanced into Saxony, and rolled its 

 bottom-moraine over the country. The interglacial gravels 

 were then ploughed out in many places, and their materials 

 thus became incorporated in the second boulder-clay. 



The drift-deposits of Holstein and Denmark, like those of 

 Germany, are divided into Upper and Lower Diluvium. Each of 

 those countries contains an upper and a lower boulder-clay, 

 separated by intervening deposits of gravel, sand, and clay. At 

 Fahrenkrog in Holstein a clay between the upper and lower 



