AND PORTO SANTO. 69 



I have before remarked, that the ridges of basalt diverge 

 from the more central heights behind Funchal, descend boldly 

 to the sea Uke the gigantic buttresses of some vast interior moun- 

 tain, and so distinctly indicate the courses of those igneous 

 streams which enveloped the island, that they would almost seem 

 to have been arrested and indurated as they flowed, as an evidence 

 to future ages. The hills and vallies which existed in the pri- 

 mitive island, at the time of the basalt first breaking through, 

 and flowing over it, and the frequent slips of the first deposits 

 of tufa under the superincum.bent weight of basalt, must have 

 contributed still more, than the long continued action of torrents, 

 to its present appearance, and to the unequal depths of the strata. 

 The variation in the sections and aspect of the island, seem to 

 me, to be explained by the considerations, that there has been 

 evidently more than one eruption (from the different alternations 

 and varieties of the basalt, tufa and scorise) ; and that, in the second, 

 streams of basalt must in some places have pursued, from the very 

 mouth of the crater, and in otbers have been diverted into, a 

 different course or direction to that of the former streams, which 

 must occasionally have presented themselves as obstacles or bar- 

 riers". The same reasoning, confirmed by similar evidence, 



face of the ocean, and afterwards lifted up, instead of forcing itself through, and flow- 

 ing over a pre-existing formation, we should not, I conceive, find such a striking 

 continuity in the basaltic coulies and ridges ; we should be luiable to trace them to 

 that central point in the interior of the island from which they have evidently pro- 

 ceeded; and the different beds of tufa near the sea, instead of presenting such a 

 regular appearance, and such a continued horizontal drift Une, (Plate 3, A.) would be 

 generally distorted and confused. Some more recent formation (perhaps a fossil 

 limestone) would probably be found immediately beneath the basalt at St. Vicente, 

 instead of the regular bed of transition limestone. 



" It appears to me, that the only alternative to this more probable and simple con- 

 clusion, is, to infer, from finding the tufa intersected by the dikes laying above the 

 compact basalt in the highest parts of the interior of the island, that wherever the 



