52 EXCURSIONS IN MADEIRA 



ginal structure of Madeira, and preceded its new form. The rock 

 directly in contact with, and above the limestone, looked in some 

 parts like a conglomerate of small nodules of basalt, imbedded in 

 an indurated tufa, with stripes and patches of lime ; but it lost 

 this character two or three feet above the limestone, and became a 

 simple rock, of a chocolate brown, and greyish red, with lines of 

 buff, losing all effervescence, and somewhat of a slaty structure. 

 Its entire depth, however, was only 4| feet, and the heights above, 

 which rise to nearly 1000 feet more, were composed (as far as I 

 could judge without ascending them, which was impossible) of 

 beds of basalt and tufa, intersected by basaltic dikes. The altered 

 basalt of the dikes intersecting the limestone, would perhaps be 

 called wakke in the cabinet, having acquired a broAvnish hue, and 

 its specific gravity being reduced to 2.7 or 0.2 less than that of the 

 ordinary compact basalt of Madeira. The unknown cause which 

 threw up the vast masses of basalt and tufa, which now envelope 

 the island so deeply, that it seems to be exclusively composed of 

 them, must have resided far beneath this bed of transition lime- 

 stone. 



I reached the middle of St. Vicente, or rather Sta. Magdalena, 

 which seemed to be a separate village, by four o'clock ; and having 

 rested a httle, I determined to follow the banks of the torrent to 

 the sea, which did not appear to be more than two miles distant. 

 The vines, trained around the lofty chestnut trees, crossed the 

 road from one to the other, interlacing like a natural trelUs work, 

 to shelter the road from the sun, and reminding me of the creep- 

 ing plants which connect whole forests in Africa. The two 

 villages nearest the sea, seemed neater and better built ; that in 

 the hollow was sheltered from the north wind by a natural wall 

 of tufa, and contained a good church, with a very snug looking 

 house for the vicar adjoining, which seemed to promise a clean 



