The children of Ishmael and other grandchildren of “Father Abraham” also wandered down, and before the time of David the zigzag lines of the caravans that carried costly merchandise from Persia and India were all over Arabia. The single-track roads were as thick as the wrinkles on an old man’s forehead. But the great trunk lines were three: one of them extended from Aden on the far south, which was the chief harbour, along the whole western stretch of Arabia to Egypt. This was the road which the Queen of Sheba took when she came to see Solomon in all his glory. The other road extended from Babylon across the desert to Damascus, the oldest city in the world; and the third caravan route, nearly as important as the other two, went slant-wise from the mouth of the Euphrates River to the old capital of the Queen of Sheba, Marib. These three great railroads of the desert were busy day after day and month after month and year after year for many centuries. Great cities sprang up beside these camel tracks, and the ruins of Tadmor still show the wonderful importance of old time Arabia. But for one reason and another trade chose other channels, and Arabia lost its importance. When the Wise Men came from the East to Bethlehem’s Manger the trunk lines were still in existence, but soon after Mohammed’s birth other parts of the world became more important, and Arabia became less and less known except to those who live in its deserts. It had to be rediscovered in the present century, and the story of the rediscovery of Arabia is full of interest. This story, also, is a story of zigzag journeys. Some bold travellers in Europe were anxious to visit the birthplace of Mohammed and see the holy city of Mecca, and at the risk of their lives, men like Burckhardt, Burton and others reached Mecca and Medina, travelling with the Arab caravans and dressed as Moslem pilgrims. In 1862 Palgrave made his celebrated journey across Arabia from west to east. And in 1876 Doughty, one of the bravest travellers, made his long and difficult zigzag journeys through Northwest and North Arabia, often in danger of his life. Suffering hunger and thirst with the Bedouins, he was driven from place to place until he finally got out of the interior safely. Even earlier than these well-known travellers were the journeys of Cursten Niebuhr in Yemen. In 1763 he was sent by the King of Denmark to explore the unknown peninsula, and set out with five companions. After many wonderful adventures he came back, but he was the only one of the five: the others died in Arabia through fever or on the voyage.