20 VOYAGE TO SPITZBERGEN. 



over a stratum of clay. The cultivated parts con- 

 sist generally of a mixture of clay and small stories. 

 In some places there is abundance of tough clay, 

 similar to that used in Britain in the manufacture 

 of bricks or pottery. 



No coal has hitherto been discovered in these 

 Islands, but in several of them are found limestone, 

 freestone, rock-crystal, corals, white spar, iron-ore, 

 copper-ore, sulphur, fuller's earth, and veins of va- 

 riegated jasper. 



Springs of fresh water are frequent in the moun- 

 tains ; and there are numerous lakes and streams, 

 abounding in salmon, trout, &c 



Along the shores are a great many ancient 

 towers, originally known by the names of Burrows 

 or Duns ; but by the inhabitants they are now 

 called Wart or Wardhills. They were so arrang- 

 ed, that the whole Islands could, by signals from 

 one to another, be apprised of approaching dan- 

 ger in a very short time. Sometimes they were 

 used for state prisons. Vid. Baxter, Gloss. Antiq. 

 Brit. 



Some of these are surrounded with dry ditches, 

 others with walls. I saw one in Unst, called Sna- 

 burg, which has both a wet and a dry ditch. One 

 of these ditches is cut with great labour through 

 the solid rock. 



