50 EXCURSIONS IN MADEIRA 



pointed at not finding the dicksonia mentioned by the above 

 author, or a single arborescent fern. The basalt and tufa dip to 

 the north, beyond the ridge separating the two Courals, and con- 

 tinue to do so all the way to St, Vicente. The compact basalt is 

 still uppermost, and its depth is considerably greater than at the 

 water-side ; the lower masses are occasionally in an advanced stage 

 of decomposition, apparently from the effect of the springs issuing 

 out of them. From the deflections of the streams of basalt and 

 deposits of tufa, (principally on account of the hills and valleys 

 of the primitive island, which have also caused the great variations 

 in the depth of the basalt, and of the existence of which we shall 

 find positive evidence at St. Vicente,) the dip, though generally 

 rapid, frequently varies, and consequently we form the best idea 

 of its great incUnation towards the sea, by recollecting, that the 

 same beds of columnar basalt and red tufa, which are not 100 feet 

 above the water, close to the beach, are found at a height of 4500 

 feet in the interior, and that at an horizontal distance of only 7-| 

 geographical miles, or 46,843 feet from the sea, which gives an angle 

 of 6" 17'. As you approach St. Vicente, you discover dikes de- 

 scending through the tufa, and the basalt which composes them 

 is full of crystals of basaltic hornblende, and occasionally of py- 

 roxene : I must own, however, that I could not have distinguished 

 the latter, either by its lustre or conchoidal fracture. The descent 



each frond rises on a slender black stem, and sometimes to a considerable height- 

 The A. hirsutum resembles a fern found by Olivier in Candia, and not yet named. I 

 have, therefore, given mine the above appellation, from the thick short hair at the 

 back of the fronds. The two following species I believe to be quite new. 



Genus Lomaria? — Frondibus linearibus, semicylindricis, uni-nervatis. Fructih- 

 catione totum frondis discum tegente. Tegumine intra dehiscente. Sp. L. sernicy- 

 lindrica. B. Genus Aspidium. — Fronde simplice, foliis obliquis oblongis. Fructif. in 

 lineis brevibus, marginem foliarum tectente, folliculis anello elastico circumdatis. Sp. 

 Asp. lobatum, B. I have recognised this fern in Vaillant's herbier, but it was not named. 



