Only where, at considerable intervals, some rivulet, fed by a glacier or a small mountain lake, issues from the ravines of the Andes to lose itself after a short course in the Pacific, green belts, like the oases of the African desert, break the general monotony, and appear more charming from the contrast with the nakedness of the surrounding waste. The planter carefully husbands the last drop of water from those scanty streams; for, as the tribes of the Sahara can only, by dint of constant industry, preserve their date-palm islands against the waves of the surrounding sand-sea, thus also the inhabitant of the Peruvian coast can only by perpetual irrigation protect his plantations from the encroachments of the neighbouring desert! But the fruits which he reaps and garners are very different from those which are produced by the African oasis; for, while none of the plants of the Peruvian sand-coast has ever found its way to the Sahara, the sycamores and tamarinds of the latter are equally unknown on the eastern shores of the Pacific. Cotton and sugar, maize and batatas, manioc and bananas, here take the place of the date-palm of the Arab, and thrive only so far as the limits of irrigation extend. In the surrounding wastes, where for miles and miles the traveller meets no traces of vegetation, and finds not one drop of water, the mule performs the part of the African camel; for, satisfied with a scantier food than the horse, it more easily supports the fatigues of a prolonged journey through the sand, and in Peru is fully entitled to be called the _ship of the desert_. The horse cannot support hunger and thirst longer than forty-eight hours without becoming so weak as hardly to be able to carry its rider; and if the latter is imprudent enough to urge it on to a more rapid pace, it falls a victim to his obstinacy, as it will obey the spur until it sinks never to rise again. Not so the mule, which, on feeling itself unable to advance, stands still, and will not move an inch until it has rested for a time; after which it willingly continues its journey. Yet, in spite of these excellent qualities, many mules succumb to the fatigues and privations of the desert; and as in the Sahara the caravan-routes are marked by camel-skeletons, so here long rows of mule-skulls and bones point out the road along the Peruvian sand-coast. Woe to him whom a shipwreck casts on these desolate shores; for he is almost inevitably doomed to destruction! In general, a healthy man can withstand hunger and thirst during four or five days, but only in a temperate climate and when the body is at rest; while in the burning deserts of Peru, the want of water during forty-eight hours, combined with the fatigue of wading through the deep sands, can only end in death. Thirst can, undoubtedly, be supported ten times longer in the moist sea-air than in the thoroughly desiccated atmosphere of a tropical waste.