24? Mr. Alison's Narrative of an Excursion to the 



lava. An ascent of 500 feet took us to the extremity of the 

 beautiful zone of vines, antl at half-past si* A.M. we crossed 

 the barranco or ravine Penilla; the surface here gradually 

 began to assume a different appearance, from the vegetation 

 which clothed it being common to Europe. 



Shortly after leaving the zone of chestnuts and lupines, we 

 entered a belt of heaths which form the third region of plants ; 

 this belt is about four miles long, and a quarter of a mile 

 broad, and extends nearly across the valley of Orotava. The 

 temperature here began to decrease very sensibly ; and al- 

 though the lavas in some places were only covered with a 

 few inches of decomposed volcanic and vegetable matter, yet 

 they were clothed with a most luxuriant verdure. This is no 

 doubt to be attributed to the moisture from the clouds, which 

 frequently completely envelop even this inferior elevation 

 towards the close of the day, or before or after any sudden 

 alteration of temperature. 



Fifteen minutes after leaving the last barranco, we crossed 

 another, called Pilloni, which is rather more than 3000 feet 

 above the sea ; and soon after, we entered the Barranco del 

 Pino Dornajito, which is 34<10 feet above the sea*; it is so 

 named from an enormous pine-tree that grew near the west- 

 ern side of the ravine. It is said that this tree was full-grown 

 at the time of the conquest of the island, 360 years ago ; — thus, 

 having stood the storms of so many ages, it was at last swept 

 into the ravine by the dreadful waterspout that devastated 

 the island on the 7th of November 1826. Although this tree 

 is partly destroyed by its fall, yet it still measures 128 feet in 

 length, and 30 in circumference. 



Under a precipice in the middle of the ravine is a small 

 spring of water, with a wooden cross at the side of it ; the tem- 

 perature of the spring was 56°, but it appears to vary more 

 than any other which I have examined, as in October the 

 temperature of the water was 65°'5. At the time of the be- 

 fore-mentioned waterspout, a body of water, some hundred 

 feet wide and thirty or forty deep, fell over this spring and 

 cross without doing it the least damage ; which the peasantry 

 attribute to the Divine interposition, forgetting that the water, 

 in falling from the height above, would form a curve and ef- 

 fectually protect it from injury. 



From the great depth of this ravine, the various strata of 

 lava can be observed ; the superior stratum consists of decom- 



* According to a barometrical admeasurement made by Humboldt and 

 calculated by the formula of Laplace. 



posed 



