34 



GEOLOGY. 



sand down. As a dune ridge along a coast travels inland, another may 

 be formed behind it. Successions of dune ridges are thus sometimes 

 formed. 



Fig. 16. — Diagram illustrating the migration of dunes on the Kurische Nehrung. 



(Credner.) 



A remarkable instance of the migration of a sand dune is recorded 

 on the Kurische Nehrung on the north coast of Germany. The Nehrung 

 consists of a long narrow neck of land composed of sand, lying off the 

 main coast. At the beginning of this century there was a notable 



Fig. 17. — Migration of dunes into a timbered region. Dune Park, Ind. Head of 



Lake Michigan. (Meyers.) 



dune ridge on one side. Since that time it has migrated a considerable 

 distance, and in its migration it has been brought into the relation- 

 ships illustrated in the accompanying diagrams (Fig. 16). In 1800 



