404 



INSULAK FLORAS AND FAUNAS WITH 



[Ch. XLI. 



uplifted in various islands to great heights, especially in the 



Made 

 times reach elevations of from 



level of the sea. 



ovement 



very gradual, and went on during the whole period which 

 witnessed the piling up on these islands of several thousand 

 feet of basaltic and trachytic lavas, just as I have described 



Marine 

 Mount 



lation of the subaerial superstructure of the great cone.* 



Nowhere could I detect, in any of the Atlantic islands 

 Avhich I visited, any signs of subsidence, or even of the tern- 



submer 



Madeira 



there are hundreds of thin horizontal layers of a red-brick 

 colour, dividing those sheets of ancient lava which are seen 

 in the sea-cliffs or in precipices in the interior. They exactly 



mould 



described (p. 13), as Having been overflowed in tbe year 1669 



tbem 



formed 



They bear testimony to the reiterated obliteration and renewal 



unaccom 



mero-ence or the intervention of the sea. 



movements 



seem 



limits of the separate islands in 



marine 



The 100 fathom 



t 



depth of water increases very rapidly, so that it is highly 

 improbable that any of the principal islands were uuited 

 and afterwards disjoined. Madeira would, indeed, be con- 

 nected with the Dezertas,t if the sea was to sink 100 fathoms ; 

 but there is no geological reason for presuming that the 

 intervening ridge, over which there is, in one part, more 

 than 400 feet of water, ever formed an unbroken isthmus 

 joining Chao to the south-eastern extremity of Madeira. 



The great antiquity of the Canaries and Madeiras is at- 

 tested by the twofold evidence of the height and magnitude 



themselves 



* Vol, ii. p. 5. 



f See Map, p. ,405, 



i See Map. 



