AND PORTO SANTO. 51 



to St. Vicente, though scarcely two miles, is more fatiguing than 

 the whole journey, being very steep, and covered with blocks of 

 basalt. The high range on the left is full of basaltic dikes, pro- 

 jecting hke buttresses from the tufa, and mantled with evergreens ; 

 they have evidently descended from the Poul, and are frequently 

 in such an advanced stage of decomposition, as to be sectile, 

 acquiring an orange yellow colour. The first village is miserable, 

 and is about 3| miles from the sea. I turned to the eastward, 

 towards the towering basaltic rocks which appeared there, and 

 after walking about two miles through vineyards, and gardens of 

 orange trees, and crossing two torrents, the one by a tottering 

 bridge, I ascended for about half an hour by a rugged winding path, 

 and found a similar limestone to that which I have before described, 

 beneath the basalt at Lisbon. Generally speaking, however, it is 

 of a whiter colour, more crystaUine in its ^;exture, contains very 

 little imbedded siUceous matter, and scarcely any compact masses ; 

 yet from analogy, and from the great depth of the bed, (being 

 nearly 700 feet from its junction with the superincumbent basalt, 

 to my last ghmpse of it in the bed of the torrent, nearly level with 

 the sea,) without a single alternation, I have no doubt of its 

 being transition, rather than primitive limestone ; its more crys- 

 talHne texture is probably owing to its vicinity to the basalt. The 

 drift hne of the junction is horizontal, and the Hmestone has 

 evidently been deposited regularly and tranquilly, without the 

 smallest trace of disturbance or confusion. Continuing about a 

 furlong to the northward, and descending a water-course, (about a 

 mile in a direct hne from the beach,) I fovmd chkes of decom- 

 posing basalt intersecting the hmestone, which, from their form 

 and direction, I should say had evidently descended from above, 

 and, instead of filhng up from below, had flowed into the gaps 

 created in the limestone by the convulsions which rent the ori- 



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