The Sahara was the scene of some of the most brilliant achievements of nineteenth-century exploration. The heroic period of individual accomplishment gradually gave place to one of more comprehensive and co-ordinated effort. Saharan exploration entered into the new phase about 1880, when France in the west began by successive stages to establish her military domination over that portion of the Sahara south of Algeria. England to the east had established herself in Egypt; and the British Geological Survey of Egypt was undertaking an investigation of the Oriental Sahara, which has resulted in the publication of many valuable maps and monographs on that region, particularly on the oases of the Libyan Desert. In an almost exact prolongation of the Sahara will be found the “Azores maximum,” a belt of barometric high pressure which stretches across the ocean.