198 Mr. Alison's Narrative of an Excursion to the 



air over the great African Desert, which is wafted by the east 

 wind to TenerifFe, and the rest of the Canary Islands. 



But this extensive, prospect astonished more than it pleased 

 me, and I felt unsatisfied from not being able to see some 

 boundary to the horizon. When we first attained the top, the 

 atmosphere below was rather hazy, which in some degree 

 confined the boundary of the horizon; but the islands of Grand 

 Canary, Palma, Gomera, and Hierro were distinctly visible, 

 and we had a complete bird's-eye view of the island below. 

 The fertile plain of Laguna, more than seventeen square miles 

 in extent, with the picturesque valleys, which slope up from 

 the sea on all sides, had the appearance of a narrow belt 

 of verdure round an immense ring of volcanic matter, with 

 the mountain upon which I was placed rising nearly in the 

 centre. 



You naturally began to look for the crater whence these 

 fiery torrents issued; — from the position of the Peak it was 

 evident that little, if any, of the devastation proceeded from 

 that source. From a careful observation of the Canadas, I 

 have no doubt that they were the cause of the surrounding 

 desolation, and that they formed an immense crater to an an- 

 cient volcano. 



It is possible that volcanic fires had existed in the island in 

 its primitive state, and at last the crust that confined them had 

 burst in its weakest part, which would most probably be in the 

 centre, nearly the present situation of the Canadas. The form 

 of them is nearly a half-circle, surrounded from the E. by N. 

 to the W.S.W. by an uninterrupted circular chain of moun- 

 tains, rising like a wall in some places to the height of nearly 

 1000 feet above the surface. On the north side is a part of 

 the same circular chain, but with a wide chasm, which sepa- 

 rates it from the other : this part is called the Risco de la Forta- 

 leza and El Cavison. From the outer part of this chain spring 

 several high ridges of mountains like buttresses to it, forming 

 fertile valleys between; — to make use of a familar illustration, 

 the Canadas may be likened to a half-wheel, the nave being the 

 Canadas, and the spokes the ridges of mountains diverging from 

 it. From that part of the chain called La Fortaleza and El Ca- 

 vison, springs a high ridge, the upper part of which is called 

 Tigayga, which running to the sea forms the western boundary 

 of the valley of Orotava. From the east side of the unbroken 

 chain runs another high ridge, called Pedrogil, La Florida, 

 and La Resbala, which form the eastern limit of the same 

 valley. On the south-east is another ridge, which is divided 

 into several branches, and on the south is part of one which 



no 



