Although to the ordinary non-scientific person the idea that most land was once beneath the sea, and nearly all rocks were formed beneath the water, may be known, yet unfamiliar, no one can land on these coral shores without being specially and personally impressed by the fact that, as the ground is entirely formed of corals and shells it has been raised up from the sea, beneath which it was formed. One may walk about on a limestone hill in England and, by patient collection of fossils, partially corroborate the geologist’s assertion that the whole thing is a mass of ancient shells, squeezed together and finally thrust up from the sea bottom, but here, so fresh are the shells, so familiar their forms and so abundant the coral, often complete in all its delicate detail[70] (like those figured opposite pages 88 and 91) that every man may be his own geologist and assert the origin of the rock as a matter of personal knowledge. Further, he may assert that all the shells and most of the corals[71] are exactly like those now living on the Red Sea reefs, and so deduce the fact that the uplifting of the original coral reef has been geologically recent, long ages since the successive worlds of species of animal whose remains make up the older, and to British minds, more usual, limestones had, one after another, passed away and been finally replaced by the inhabitants of our own world. It is one of the most recent of rocks, and yet it gives some idea of the meaning of the expression “Geologic time” to remember that these very ordinary-looking shells lived thousands of years before the builders of the pyramids. We can better appreciate the raw newness of the Red Sea cliffs if we digress a little to the comparison with the very different rocks of Equatorial East Africa and elsewhere which have however much the same origin. These latter are much more typical of elevated coral the world over, the Red Sea, owing to its nearly rainless climate, having peculiarly well preserved the corals of its raised reefs. Plate XXXV of cliffs in Zanzibar should be compared with the Red Sea rocks on Plates XXXII and XXXVII, and the comparison made in Chapter VIII, page 111, referred to. Of course the differences between the elevated coral of the Equatorial coast and that of the Red Sea might be due to the former being of greater age; though, if such a difference exists, as it is not considerable[72], we are led to lay more stress on the different physical conditions under which they are placed. These are that the equatorial rocks are exposed to a considerable rainfall, and, owing to the tides, to far more drenching by spray than are those of the Red Sea, resulting in the solution of the surface layers of the rock and the crystallisation of the dissolved limestone in all the cavities of the interior, thus making the rock both crystalline and homogeneous within, as before described.