28 
per ore, sulphur, fuller’s earth, and veins j 
of variegated jasper. 
Springs of fresh water are frequent in 
the mountains; 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 
name of Burrows or Duns; but by the 
inhabitants they are now called Wart or 
Wardhills. They were so arranged, that 
the whole Islands could, by signals from 
one to another, be apprised of approach¬ 
ing danger in a very short time. Some¬ 
times 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 Snaburgh, which has both a 
wet and a dry ditch. One of these 
ditches is cut with great labour through 
the solid rock. 
There is another in Fettar, (one of the 
