We have no ports of call on these desert coasts, so make 46 straight for the exit into the Gulf of Aden and the wide Indian Ocean. As we near the southern end of the Sea, the water grows shallower, its shores approach again, and we can see bare brown rock on either hand, which makes the blazing sun seem even hotter than before. On our left, off a jutting corner of the Arabian coast, lies a low bare island, Perim. It is without vegetation or water, its sole virtue consisting in a deep harbour, commanding the narrowest part of the outlet, where the channel is only about twelve miles across. We occupied it as a precaution, fifty years ago, and it is now a coaling and cable station, with a small military guard. But it is without fortifications, and in spite of its position it is not the real key to the Red Sea; we must look for this in Aden, a hundred miles further east, just as we found in Gibraltar the control of the strait to the westward. [Illustration: ADEN.] Aden proper is a small peninsula, five miles by three, lying 47 across a narrow isthmus which links it with the mainland. Thus it is not unlike Gibraltar; but one end of the peninsula, instead of jutting into the open sea, stretches westward towards another peninsula, that of Little Aden, which helps to enclose a large bay. Little Aden, the coastline and the mainland for a short distance inland were all obtained by purchase during the latter part of the nineteenth century; and the whole of the country behind, south of a line drawn northeastward from the coast opposite Perim, is a British Sphere of Influence. North of the line is the territory of Turkey. Aden is thus made secure from hostile approach on the land side. If we imagine the area of Gibraltar to be extended all round the bay of Algeciras and inland to the hill country of Spain, the position of the two fortresses would closely correspond.