[58]In some lagoons quantities of sand are formed of great numbers of the minute shells of lowly organisms, the foraminifera. This is, of course, a very different thing to that resulting from breaking up of coral and shells.
[59]1912 was a rich year! 40 millimetres fell on Oct. 22nd and 20 millimetres in December, about 2½ inches altogether.
[60]J. W. Gregory, The Great Rift Valley, John Murray, 1896.
[61]The ranges bordering the sea are from 4000 feet to 8000 feet high, but of course were much higher in the days when the Rift opened.
[62]Recently, that is, geologically speaking.
[63]Such ring-shaped reefs, rising out of deep water, are termed Atolls. Sanganeb is a small example compared to those of the Indian and Pacific Oceans.
[64]I have marked other harbours as they are interesting geologically, but there are only three miserable villages on this whole coast in addition to the two towns. There is no village at Trinkitat, but the cotton from Tokar is loaded on to sambûks here.
[65]I.e. hills of Archean, ancient rock, as opposed to the newer sandstones, gravels and limestones.
[66]The Eastern Desert of Egypt, southern section, describes a part of the Red Sea coast range north of the Sudan boundary, but essentially similar to the rest.
[67]Two borings, made in the hope of obtaining water two miles inland, near Port Sudan, were carried down through 300 metres, nearly 1000 feet, of this kind of material.