The long repose and seclusion of Central Arabia was first broken during the present century. It may be well to state, very briefly, the circumstances which led to it, since they will explain the great difficulty and danger which all modern explorers must encounter. Early in the last century, an Arabian named Abd el-Wahab, scandalized at what he believed to be the corruption of the Moslem faith, began preaching a Reformation. He advocated the slaughter or forcible conversion of heretics, the most rigid forms of fasting and prayer, the disuse of tobacco, and various other changes in the Oriental habits of life. Having succeeded in converting the chief of Nedjed, Mohammed Ibu-Savod, he took up his residence in Derreyeh, the capital, which thenceforth became the rendezvous for all his followers, who were named _Wahabees_. They increased to such an extent that their authority became supreme throughout Central Arabia, and the successor of Ibu-Savod was able to call an army of 100,000 men into the field, and defy the Ottoman power. In the year 1803 the Wahabees took and plundered Mecca, and slew great numbers of the pilgrims who had gathered there. A second expedition against Medina failed, but the annual caravan of pilgrims was robbed and dispersed. Finally, in 1809, the Sultan transferred to Mohammed Ali, of Egypt, the duty of suppressing this menacing religious and political rebellion. The first campaign in Arabia was a failure; the second, under Ibrahim Pasha, was successful. He overcame the Wahabees in 1818, captured Derreyeh, and razed it to the ground. In 1828 they began a second war against Turkey, but were again defeated. Since then they have refrained from any further aggressive movement, but their hostility and bigotry are as active as ever. The Wahabee doctrine flatters the clannish and exclusive spirit of the race, and will probably prevent, for a long time, any easy communication between Arabia and the rest of the world. The greater part of our present knowledge of Arabia has been obtained since the opening of this century. The chief seaports and the route from Suez to Mt. Sinai were known during the Middle Ages, but all else was little better than a blank. Within the last fifty or sixty years the mountains of Edom have been explored, the rock-hewn city of Petra discovered, the holy cities of Medina and Mecca visited by intelligent Europeans; Yemen, Hadramaut, and Oman partly traversed; and, last of all, we have a very clear and satisfactory account of Nedjed and the other central regions of Arabia, by the intrepid English traveller, Mr. Palgrave.