28(5 Sketch of the Geology of Madeira. 



of its barrier bills are formed of columnar basalt ; licrc and 

 there rising to a peak, or broken into what might be tevniecJ 

 a crvstallized ridge, or tapering to a point like the granite 

 needles in the Mer de Glace. The eohnnnar strata are 

 foiind here in all directions. They rlip usually to the sea, 

 but occasionally arc dislocated in the most abrupt manner. 

 Dvkes of lava, rising perpendicularly to the iiorizon, inter- 

 sect the strata at right angles. I saw one 200 or 300 feet 

 ill hei«ht, which cut tnrouuh several of the alternations of 

 the red and gray lava. This valley of the Corral \x^\\ merits 

 the most alieniive examination ; yet the journey there is 

 one of some labour, and the walk down the river that flows 

 in its bottom so difficult and toilsome, as almost to deter 

 every one from the undertaking. We left the town of Fun- 

 chal soon after day-break, and did not return till between 

 ciglit and nine at night, having been, during the wliole of 

 that period, in a state of incessant exertion on horseback 

 or on foot. The bed of the valley itself cannot be descended 

 on muks or on horseback. 'l"he walk is ei>:ht or nine miles 

 in length, and you are compelled to clamber over rocks, as 

 there is ncit even a track, or wade in the bed of the river, 

 which is rapid, and full of large and pointed stones. Some 

 of the highest hills of the island border on this valley. 

 Several of them rise from the bed oi the river in a perpen- 

 dicular height of 1000 or 1300 feet, judging only by the 

 eve, and arb what the Fiench term taitU a pic. Others are 

 broken into a succession oi steep descents, and are covered 

 with forests of wood and a profusion of plants. Dowii 

 many there fall small cataracts of water, and some are hol- 

 lowed into deep recesses, whence issue from the lava nu- 

 itierous little streams that contribute to swell the principal 

 river in the valley. 



As you arrive on the brink of the Corral, after a ride of 

 about ten iTiiks from Funchal, you find yourself suddenly 

 on the ediic oi a precipice, near to which a sort of traversing 

 ^tair-c;isc is cut, with a track winding to the bottom. On 

 the right is a wall of lava nearly perpendicular from 400 to- 

 500 feci in depth, composed of the two species of the red 

 and trray, alternating five or six times, and assuming in its 

 dislocation the form of a bow, boih the lavas following in 

 a resrular bend the shape of the curve. 



On the lett of the stairs by which you are to descend^ 

 innumerable small columns of the gray lava project from 

 t-lie side: ihev dip N.W. and their iorm in general is qua- 

 drangular; but i found several ofihem in prisms of three, 

 live, and six sides. They arc remarkably small, and as 



they 



