38 



GEOLOGY OF MADEIRA* 



Its Tallies, 



Size of the 

 island. 



puis, 



Vallies. 

 Surface day. 



Extinct vol- 

 canues. 



nomena wliich the strata in that island exhibit, the following 

 observations may not peiliaps he who] y i.nacceptable. Th< y 

 may be ronsidered as furnishing; direc'ions to others, vviiere 

 to look for some of the most iuterestinif ol>je(.is; and may 

 afford to future travellers a email portion of the information^ 

 which my guide, Dr. Shnter, so liberally comnnin-.tated to 

 me. That gentkman, having long resided in theislan<i, had 

 repeatedly traversed it, and was thereby able to point out to 

 me some of the rircumstances which were most worthy of 

 examination, particularly the nature of the various siiata that 

 are exposed to view in the deep and abrupt vallies which in- 

 tersect the island in all directions. These vallies are no less 

 picturesque to the eye of the common traveller than tht.y are 

 deserving of the attention of the geologist. They are m ge- 

 neral narro'v and deep, the summits oi the hills that form 

 their boundaries are broken into |}eyks, rugged and bare, 

 while their sides are covered with the cedar and other trees 

 peculiar to southern latitudes, and with a profuse variety of 

 shrubs and plants, among which the erica arborea is the most 

 beautiful, and in the greatest quaniiy. 



The island of Madeira {though i believe it never has been 

 surveyed) is said to be about 50 miles in length, and in its 

 broadest part abcut 20, but the average breadth does not 

 exceed 15 miles. 



It consists of a succession of lofty hjUs rising rapidly from 

 the sea, particularly on the eastern and northern extremitieis. 

 The summits of many of these ranges present the appearance 

 of what has been called a table laud; yet occasionally the 

 forms are conical, and surmounted by a peak, which in some 

 instances I found to be of <'olumnar basalt. Deep ravines 

 or vallies descend from the bills or serras to the sea, and in 

 the hollow of most of them flows a sm II rivcr, which in ge- 

 neral is rapid and shallo , Th soil oft e island is clay on 

 the surface, and large masses of it as hard as brick are found 

 underneath. Though there are not at present any existing- 

 volcanoes in the island, yet the remains of two craters are to 

 be Keen, one on the e stern the other on the western side, 

 the largest being about a Portuguese league, or four English 

 miles in circumference. Every thi g around wears ma Vs 

 pf haying suffered the action of fire, yet I was unable to dis- 



cove 



