In consequence of this structure, the Camel sinks less deeply into the ground than any other animal; but yet it does sink in it, and dislikes a deep and loose sand, groaning at every step, and being wearied by the exertion of dragging its hard foot out of the holes into which they sink. It is popularly thought that hills are impracticable to the Camel; but it is able to climb even rocky ground from which a horse would recoil. Mr. Marsh, an American traveller, was much surprised by seeing a caravan of fifty camels pass over a long ascent in Arabia Petræa. The rock was as smooth as polished marble, and the angle was on an average fifteen degrees; but the whole caravan passed over it without an accident. The soil that a Camel most hates is a wet and muddy ground, on which it is nearly sure to slip. If the reader will look at a Camel from behind, he will see that the hinder legs are close together until the ankle-joint, when they separate so widely that the feet are set on the ground at a considerable distance from each other. On dry ground this structure increases the stability of the animal by increasing its base; but on wet ground the effect is singularly unpleasant. The soft, padded feet have no hold, and slip sideways at every step, often with such violence as to dislocate a joint and cause the death of the animal. When such ground has to be traversed, the driver generally passes a bandage round the hind legs just below the ankle-joint, so as to prevent them from diverging too far. It must be remarked, however, that the country in which the animal lives is essentially a dry one, and that moist and muddy ground is so exceptional that the generality of Camels never see it in their lives. Camels do not object to mud an inch or two deep, provided that there is firm ground below; and they have been seen to walk with confident safety over pavements covered with mud and half-frozen snow. The animals can ford rivers well enough, provided that the bed be stony or gravelly; but they are bad swimmers, their round bodies and long necks being scarcely balanced by their legs, so that they are apt to roll over on their sides, and in such a case they are sure to be drowned. When swimming is a necessity, the head is generally tied to the stern of a boat, or guided by the driver swimming in front, while another often clings to the tail, so as to depress the rump and elevate the head. It is rather curious that the Camels of the Sahara cannot be safely entrusted to the water. They will swim the river readily enough; but they are apt to be seized with illness afterwards, and to die in a few hours. We now come to some other uses of the Camel.