“I have seen many ancient volcanoes, and have given descriptions of several superb basaltic causeways and delightful caverns in the midst of lavas; but I have never found any thing which comes near this, or can bear any comparison with it, either for the admirable regularity of the columns, the height of the arch, the situation, the forms, the elegance of this production of nature, or for its resemblance to the masterpieces of art, though this had no share in its construction. It is therefore not at all surprising that tradition should have made it the abode of a hero.
“This amazing monument of nature is thirty-five feet wide at the entrance, fifty-six feet high, and a hundred and forty feet long.
“The upright columns which compose the frontispiece, are of the most perfect regularity. Their height, to the beginning of the curvature, is forty-five feet.
“The arch is composed of two unequal segments of a circle, which form a sort of natural pediment.
“The mass which crowns, or rather which forms the roof, is twenty feet thick in the lowest part. It consists of small prisms, more or less regular, inclining in all directions, closely united and cemented underneath, and in the joints, with a yellowish white calcareous matter, and some zeolitic infiltrations, which give this fine ceiling the appearance of mozaic work.
“The sea reaches to the very extremity of the cave. It is fifteen feet deep at the mouth; and its waves, incessantly agitated, beat with great noise against the bottom and walls of the cavern, and every where break into foam. The light also penetrates through its whole length, diminishing gradually inwards, and exhibiting the most wonderful varieties of colour.
“The right side of the entrance presents, on its exterior part, a vast amphitheatre, formed of different ranges of large truncated prisms, the top of which may be easily walked on. Several of these prisms are jointed, that is, concave on the one side, and convex on the other; and some of them are divided by simple transverse intersections.
“These prisms, consisting of a very durable and pure black basaltes, are from one to three feet in diameter. Their forms are triangular, tetrapedral, pentagonal, and hexagonal; and some of them have seven or eight sides. I saw several large prisms, on the truncatures of which are distinctly traced the outlines of a number of smaller prisms; that is, these prisms are formed of a basaltes, which has a tendency to subdivide itself likewise into prisms. I had before observed the same phenomenon in the basaltic prisms of Vivarais.
“The cave can be entered only by proceeding along the platform on the right side, which I have mentioned above. But the way grows very narrow and difficult as it advances; for this sort of interior gallery, raised about fifteen feet above the level of the sea, is formed entirely of truncated perpendicular prisms of a greater or less height, between which considerable address is necessary to choose one’s steps, the passages being so strait and so slippery, owing to the droppings from the roof, that I took the very prudent resolution, suggested by our two guides, to proceed barefooted, and take advantage of their assistance, especially in a particular place, where I had room only to plant one foot, whilst I clung with my right hand to a large prism to support myself, and held the hand of one of the guides by the other. This difficult operation took place at the darkest part of the cave; and one half of the body was at the time suspended over an abyss, where the sea dashed itself into a cloud of foam.
“I was desirous of penetrating to the farthest extremity, and I accomplished my purpose, though not without considerable difficulty and danger. I more than once found my attention distracted from the observations which I was happy to have an opportunity of making, to the thought of how I should get back again.