Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/407

 species of the red and grey, alternating five or six times, and assuming in its dislocation the form of a bow, both the lavas following in a regular bend the shape of the curve.

On the left of the stairs by which you are to descend, innumerable small columns of the grey lava project from the side; they dip N.W. and their form in general is quadrangular; but I found several of them in prisms of three, five, and six sides. They are remarkably small, and, as they lie in this bed, appear almost all to break off from each other at five or six inches in length, and I never found them exceed this size. They seem to form a dyke that cuts through the horizontal beds of lava.

At the edge of the descent there is a projection or range of basaltic columns, rising like a wall, tapering to the top, and separating into large quadrangular prisms. We found no black ashes in the valley of the Corral, though towards the bottom there are considerable strata of pumice, great masses of scoriæ, and cellular lava, and lava in a state of semi-vitrification; the whole presenting evident marks of an eruption, anterior to that which had formed these various strata of lava, which are visible from the summit of the hill to the bed of the river.

The dip of the strata is in general towards the sea. Basaltic columns shoot from the side of the ordinary strata, which are intersected by various dykes; and one of these in particular swept across both sides of the valley. There are here also rocks of about 100 feet in height, composed of a species of breccia. We examined one near the church, at the extremity of the winding stair-case, forming the descent into the valley, which was composed of large and small pieces of lava, some of them of many yards in length and depth, the angles being rounded, and the whole agglutinated together by a hard black earthy substance, that resisted all the force we could use to