AND EIVEE VALLEYS BORDERING THE BRITISH ISLES. 319 



itself when, according to Professor Hull, Iceland, the Faeroe 

 Islands, and the Orkneys consbitutod one long, narrow chain of 

 land united with the British Isles, one cannot help comparing 

 their present condition to a set of jewels of which the string has 

 got broken. 



I suppose it will be conceded that as the fauna ai-e on a small 

 scale as regards number of species in Scotland, more scanty in the 

 Orkneys, fewer still in the Faeroes, and fewest of all in Iceland, 

 the reverse is the case with regard to the altitude of the hills : the 

 highest cliffs in Iceland are up to 3,000 feet, descend sheer down to 

 the deep, and the highest mountains and rocks are just over 6,000 

 feet in altitude. Then you get several, I should judge, of 1,500 

 feet in the Faeroes and only one in the Orkneys of 1,556 feet 

 {Ward Hill of Hoy), and that is by far the highest in the whole of 

 that archipelago ; and looking back to the period that Professor 

 Hull describes, supposing the north of Iceland to be united by 

 continuous land for a distance of 500 miles with Caithness, would 

 that — the fact of continuous land — tend to produce an increased 

 number of species or a scries of fauna in the north ? I doubt 

 it ; because, when you think of the large intervening distance of 

 land — 500 miles — and that insects would have to cross from richer 

 and more varied vegetation and from trees of considerable size, 

 one doubts whether they would do so, or migrate north ; and 

 there is another very satisfactory reason, viz. : that lime trees, 

 thistles, nettles, turnips, and cabbages, are either nob found at all 

 in Iceland, or they exist in very infinitesimal quantities, and so 

 several of our common species of butterflies would not be found 

 there, or, reaching it, would not survive and multiply. You can 

 have the food plant without the insect, but you cannot have the 

 insect without the food plant. It may be true to some extent 

 that, ever since pre-historic times, the climate has been de- 

 teriorating, because there are certain indications that there were 

 more trees in Iceland in the middle ages, from the names of 

 several places commencing with the prefix of Eeydir Sorhus edulis, 

 the wild crab apple, which the outlaw may often have munched 

 in his wanderings ; and so ti'ees of considerable size may have 

 ■flourished and served for the preservation of various kinds of 

 insects. All along the course of many centuries the climate 

 may have sufFered owing to the recurrence of volcanic out- 

 breaks and through the forests having been carelessly fired by 

 the natives. N^o doubt Iceland has suffered in two or three ways 



