62 EXCURSIONS IN MADEIRA 



not consider this indurated mud-like matter, which is generally 

 charged with basaltic pebbles and fragments, as originating in the 

 decomposition of the basalt itself, but rather to have been created 

 in the crater by a different proportion of the constituent elements, 

 and to have flowed from it, intermingled with the streams of basalt. 

 The yellow tufa, which is here above the basalt, is thickly sprinkled 

 with small pumice-stones. The cassia accumlnata covers the road 

 side in all directions, mingled with cacti, pclargonia, roses, fig-trees, 

 and ivy; four or five small dragon-trees add to the variety. Having 

 ascended about 2000 feet above the sea, we meet with plantations 

 of the pinus si/lvestris, which are said to have been made, with the 

 view of binding the loose red soil, wliich would otherwise be scat- 

 tered, and slide away over the chfFs in the rainy season. The deep 

 red tufa, however, which forms this soil, and which rests on the 

 yellow, seems to be more aluminous here than on the western side, 

 and firmer ; perhaps from the number of basaltic dikes which in- 

 tersect it, running towards the sea, and generally presenting a 

 series of close horizontal fractures, as if it had not flowed very 

 rapidly into the rents of the tufa, but was deposited in layers. 

 Masses of basalt crown the tops of all the hills, but are in no 

 instance columnar; and the remnants of streams of basalt connected 

 with these masses, and descending over the tufa into the sea, are 

 constantly evident. Descending the ravine from which the path 

 to the summit of the Brazen Head branches off, the red tufa, 

 which just above it had been full of large nodules of basalt, appears 

 to be charged with a kind of pumice grit, and dips S.S.W. in an 

 angle of 30°; a natural cross section at your back, running east and 

 west, discloses this tufa in horizontal layers with the basalt above it. 

 Looking down at the Brazen Head, from the lofty cliff adjoining 

 it on the west, we observe large masses of columnar, mixed with 

 angular, irregular pieces of basalt, (sometimes scoriaceous) im- 

 bedded in red tufa. The grand slip to the south will be best 



