"The principal difference between Aldabra and other is that it seems to be of very ancient formation and has undergone an elevation of 15 to 20 feet. The island is flat, composed almost entirely of naked coral rock, rough and jagged, completely honeycombed in every direction with pits and fissures. Scarcely any soil exists, excepting where a small quantity of rich mold, formed by decomposing coral, has accumulated in hollows of the rock. The sea face is an overhanging cliff of rock, but in a few places, especially on Île Picard and on the west coast, are sandy beaches and low sand-hills. Upon the south coast are Dune Jean Louis and Dune du Mêche, sand hills, which reach 65 feet above sea level—the highest points in Aldabra. Nearly the whole surface is covered with a dense, almost impenetrable scrub of tangled bushes. No large trees now exist except the s, which attain a height of 10 feet and a diameter of a foot or more."