It was long past the middle of the day when I descended from the hill. We had no alternative but to return to the only spot where we knew water was to be had; this was now distant twenty-one miles to the north-east, so we departed in a straight line for it. I was heartily annoyed at being baffled in my attempt to reach the mountain, which I now thought more than ever would offer a route out of this terrible region; but it seemed impossible to escape from it. I named this eminence Mount Olga, and the great salt feature which obstructed me Lake Amadeus, in honour of two enlightened royal patrons of science. The horses were now exceedingly weak; the bogging of yesterday had taken a great deal of strength out of them, and the heat of the last two days had contributed to weaken them (the thermometer to-day went up to 101 degrees in shade). They could now only travel slowly, so that it was late at night when we reached the little tank. Fifty miles over such disheartening country to-day has been almost too much for the poor animals. In the tank there was only sufficient water for one horse; the others had to be tied up and wait their turns to drink, and the water percolated so slowly through the sand it was nearly midnight before they were all satisfied and begun to feed. What wonderful creatures horses are! They can work for two and three days and go three nights without water, but they can go for ever without sleep; it is true they do sleep, but equally true that they can go without sleeping. If I took my choice of all creation for a beast to guard and give me warning while I slept, I would select the horse, for he is the most sleepless creature Nature has made. Horses seem to know this; for if you should by chance catch one asleep he seems very indignant either with you or himself.