while the camels were old acquaintances. I have often made attempts to learn the age which this animal usually attains, but have never been able fully to ascertain it. The general answer is, a hundred years. By examining and tracing the traditionary stories on the subject, I am led to conceive their span of life equal to that of man, and subject to similar frequent contingencies from different causes, such as extremes of heat and cold, excessive fatigue, and particularly the great neglect of the owners. This evening I have bestowed great pains on the preservation of the water, having suspended the suspicious geerbahs in my tent. _Feb._ 18. We mounted our camels this morning at half past six, and have had an exceedingly fatiguing ride of thirteen hours, forty miles, without any repose, struggling through one immense down of sand. There were some small hills of sandstone, with occasional thin layers of gypsum. The sand was very fatiguing for the camels: on its surface I found disseminated many of the round balls of iron flint, or iron glance, varying from four to eight inches in circumference. Their exterior is often uneven. I found, also, some balls, hollow like the others, and occasionally two united together. These were silicious conglomerates. I observed, also, numerous quartzose pebbles, and some fragments of white marble, the only specimens I have seen in this desert. The mountains are chiefly of slate. We have suffered very much from the fatigue of this day’s journey, and have still five days’ march through this waterless desert. The only object to interest me, and relieve the weariness of mind and body, has been the merage, so often described. Some travellers state that this phenomenon has deceived them repeatedly. This I am surprised at, since its peculiar appearance, joined to its occurrence in a desert where the traveller is too forcibly impressed with the recollection that no lakes or standing pools exist, would appear to me to prevent the possibility, that he who has once seen it can be a second time deceived. Still this does not diminish the beauty of the phenomenon:—to see amidst burning sands and barren hills an apparently beautiful lake, perfectly calm, and unruffled by any breeze, reflecting in its bosom the surrounding rocks, is, indeed, an interesting and wonderful spectacle; but it is a tantalising sight to the Arabs traversing the desert on foot, always with a scanty supply of water, and often, owing to their great imprudence, wholly destitute of it. There is much of the sublime to elevate, and of real danger to excite the mind, in the passage of the Desert: the boundless plains of sand, the thought of the distance from the habitations of man, and from the most common necessaries of life, the perpetual apprehension of falling short of water, and the certainty, that whoever, from fatigue or illness, is unable to keep pace with the caravan, will at once, with a camel and his share of the provision, be abandoned to his fate.