After seeing the strange conveyances and modes of travel in Europe and in the civilised countries of Asia, it will be interesting to leave the beaten tracks behind us altogether for a time. We will go beyond the high roads and the railways, and find out how people make journeys in the great wildernesses of the world, where travellers must be prepared to undergo discomforts and hardships, to meet with dangers, and, very often, to carry their lives in their hands. If we open our atlases and turn to the maps of Africa, America, Asia, and Australia, we shall find that in each continent there are blank spaces. Sometimes these are called deserts or forests, but often we can only guess at the character of the country from the fact of there being no rivers marked and very few names of towns and cities. The most famous of all deserts is the Great Sahara, which extends for thousands of miles across the north of Africa. Most people picture it as a huge sandy plain, where there is no water and no sign of life or vegetation; but, in reality, although there are districts where the shifting sandhills stretch away as far as the eye can see, a vast part of the Sahara consists of a stony tableland covered with a scanty growth of low, thorny bushes. In the deserts there are, moreover, many fertile spots looking like exquisite little green islands set in the midst of a glowing, yellow sea. They are called oases, and are found where there are wells or pools of water. Arabs live in these places, cultivating the land and building mud-houses, while other tribes spend their time in wandering about the desert, seeking food for their animals and trading in the scattered towns and villages. These wanderers, or nomads, with their camels, horses, and herds of sheep and goats, may be seen slowly moving across the great sunburnt plain and pitching their brown tents at night among the sand-dunes. [Illustration: MIXED TRANSPORT IN NIGERIA.] The nomadic Arabs travel in large parties called caravans, for there are brigands in the Sahara who would rob and murder lonely wayfarers. The men in the caravan often ride, and their horses are considered the finest in the whole world. The Arabs prize these horses highly and treat them well, never allowing them to be teased by the children, and, at the end of a long day's journey, giving them their meal of milk and dates before they eat anything themselves. Horses, however, are only used for riding, and all the hard work is done by the camels, "the ships of the desert," as they are called. It is a strange sight to see a great caravan crossing the desert, sometimes as many as a thousand camels marching along in single file, each with a heavy load on his back.