The island of Zanzibar, 60 miles long by 20 wide, and 20 miles from the mainland of Africa, seems to be a part of the East African barrier system, and it certainly was separated from the mainland by the destruction of the intervening land; the shallow dividing channel being full of shoals and sandbanks formed by cutting down of islands. The fauna of Zanzibar, including leopards, serval cats, &c., can be accounted for in no other way. The Great Barrier of Australia, a thousand miles long, is the same thing on a vastly greater scale. But, as described in the next chapter, the Barrier system of the Red Sea is quite another thing, and its mode of formation may possibly be unique in the world. CHAPTER IX GEOGRAPHY OF RED SEA AND FOUNDATIONS OF THE REEF SYSTEMS _The Climate_ has already been roughly described but it is interesting enough to deal with in more detail. One might suppose the extremes of dry heat and cold of the desert climate to be moderated by the sea, and the resulting mean to be a fairly mild and equable climate. Actually we get alternations of desert and sea climates, extreme dry heat in summer and steaming winds from the sea, both bringing great discomfort. The winter from November to March is cool and pleasant so long as the prevailing north-east wind blows, but there are spells of very disagreeable weather even in winter. When the wind is from the south-east the temperature rises and at the same time it becomes very damp, saltish moisture being over everything, so that even the natives become lazy and depressed and many suffer from rheumatism, &c. One has however the satisfaction of knowing that the south-east wind usually lasts but three days or so, and never more than a week, when the north wind comes back and we revive. The south wind is generally preceded by a day’s calm and increases in strength until the end, when a short calm ushers in a very strong wind from the north. On several occasions I have actually seen the approach of this sudden and welcome change as a line of low cloud, formed by the condensation of vapour where the cold north wind meets the damp from the south. This sudden change was the cause of the wrecking of a _sambûk_ which was beating down to Port Sudan in a south-east wind. Anchoring one night in a long narrow harbour open to the north, they were caught by the north wind next morning and, being unable to beat out against it, were driven on to the reef. The crew had to walk in to Port Sudan, distant about twenty-five miles, without food or water, one of them having a badly crushed wrist. As I had cargo on the _sambûk_ I went up immediately, and after only two or three days there was nothing visible of the _sambûk_, but fragments scattered over miles of reef.