292 Mr. Ben NET on the Island of Tcncrlffe, 



worn by the rains, and there was no appearance of any other rock. 

 Leaving this forest, the track passes over a series of green hills which 

 we traversed in about two hours, and at last halted to water our 

 mules at a spot called el barranca del pino de la meruenda^ where there 

 is a small spring of bad and brackish water issuing from a lava rock. 

 The ravine is of considerable depth. After the vegetable earth, 

 which is 2 or 3 feet deep, a layer of tufa succeeds, which is fol- 

 lowed by a lava of a greyish-blue colour, 30 or 40 feet in depth. 

 It is compact, contains olivine, and the strata lap over each other, 

 but shew no appearance of columnar formation. The range of 

 green hills extends a mile or two further, the soil shallowing by 

 degrees, more lava and scoria shewing themselves on the surface, 

 the ravines or channels, worn by the rains, becoming more common, 

 the trees and shrubs gradually dwindling in size, and of them all 

 the Spanish broom alone at length covers the ground. Leaving 

 behind us this range of green hills, the track still ascending leads for 

 several hours across a steep and difficult mass of lava rock, broken 

 here and there into strange and fantastic forms, worn into deep ra- 

 vines, and scantily covered in places by a thin layer of yellow pumice. 

 The surface of the country, for miles and miles around, is 

 one continuous stream of lava ; the rents or ravines of which seem 

 to be formed partly by the torrents from the hills flowing for so many 

 ages, and partly from that tendency, characteristic of a lava current, 

 to keep itself up in embankments, and in its cooling process to open 

 out into those hollows which I have uniformly found in every 

 eruption of lava that I have had an opportunity of examining. 

 This lava is cellular beyond any I have ever seen, is of a clayey 

 earthy porphyritic composition, and contains few, if any, pieces of 

 olivine, though here and there felspar in a semlcrystallised form. 

 As we proceeded on our road, the hills on our left, though broken at 



