64 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



usually ranges between 30 and 50 fathoms, while to the 

 westward midway to the Irish coast there is a long narrow 

 trough descending to over 70 fathoms.'' 



" As at present constituted, the Island, with the 

 detached islet of The Calf off its south-wes'tern extremity, 

 contains 227 square miles (140,325 acres), of which 170 

 square miles, or three-fourths of the whole, are occupied 

 by the slate and greywacke rocks, probably of Upper 

 Cambrian age, composing the hilly massif. Strata of the 

 Lower Carboniferous age occur in a small basin of 7 or 

 8 square miles at a low elevation in the South of the 

 Island, and a narrow strip of red sandstone, probably 

 belonging to the same period, borders the coast for two 

 miles about midway upon the western side. The northern 

 extremity consists of a low-lying tract of about 45 square 

 miles, which is an addition made to the Island in glacial 

 times by the deposition of great masses of glacial drift 

 upon the pre-glacial sea-floor. Deep borings through this 

 drift have recently revealed a rock-floor of Triassic, Per- 

 mian, and Lower Carboniferous strata at a considerable 

 depth below sea-level." 



" The Island is irregularly oblong in shape, with its 

 longer axis running N.X.E. to S.S.W., which is the direc- 

 tion of strike of the slate rocks. In this direction, from 

 the Point of Ayre to Spanish Head, <the land has a length 

 of 30 miles, while the breadth of its wider central portion 

 varies from 8 to 12 miles. Excepting in the well- 

 cultivated northern plain there is little flat ground. In 

 the interior the physical features bear much resemblance 

 to the southern uplands of Scotland. The hills are steep, 

 but not generally craggy, and are arranged in long grassy 

 or heather-covered ridges running with the longer axis of 

 the Island, with broad intervening valleys. The highest 

 of these ridges commences in the vicinity of the eastern 



