AND PORTO SANTO. 7 



verbascum thapsum, until I had ascended two-thirds of the way, 

 or about 1400 feet above the sea, where they disappeared: the 

 thymus vulgaris continued a Uttle further. The scilla moritima 

 (in great beauty), the daphne gnidium (very flourishing but 

 dwarfish), the carduus acaulis, the ert/nghmi teniie, the anethum 

 segetum (which seems to start out of the clefts of every roc^, 

 yielding an unpleasant odour), continued from the foot of the 

 ascent to within a few feet of the summit. Two solitary plants 

 of the dipsacus fnllonum grew about three-fourths of the way up, 

 and just beyond them appeared the echium vulgare, thinly scat- 

 tered. 



The limestone only varied in its tints of the exterior surface, 

 which sometimes looked as if it had been covered with a mixture 

 of soot and ochre, and presented longitudinal furrows, resembUng 

 woody fibres. I discovered no fetid odour on striking the dif- 

 ferent masses, nor any trace of fossil remains ; but the nodules 

 of silex which it contained, evidently of cotemporaneous origin, 

 were frequent, and deeply impregnated with lime: occasionally 

 portions of common jasper, and, more rarely, of agate, were im- 

 bedded. About half way up, I walked over vast sheets of this 

 limestone, more compact, mottled, and seemingly harder than 

 the rest; they were hewing it into mill-stones. The hillocks 

 which bordered the ascent were formed of detached pieces of silex 

 and hme imbedded in a loose earth : there appeared to be a breccia 

 of the same nature, not only above the limestone, but in one 

 instance intersecting it horizontally, in shallow beds. In the 

 lowest rocks, especially in the quarry north of the aqueduct, the 

 mass more frequently appeared crystaUine, and once afforded 

 me prismatic crystals, the more compact masses adjoining which 

 were sometimes so happily sprinkled with green dots as to appear 

 dendritic. The highest point immediately west of the aqueduct, 

 and affording a view of the mouth of the river, still presented 



