I once took up my quarters at a small spring flowing from some granite rocks, where I remained six weeks, near the range of hills already described, to hunt and explore; this was the following year, and strange to say, every afternoon heavy masses of clouds just showed their heads above the horizon, covering more than a quarter of a circle, that is, from the west of north to east-north-east, taking up the same position daily; their lovely pink tints faded as evening advanced, no clouds could be seen, and yet nightly we had these flashes. Some may say, surely these clouds must have passed over some portion of the desert, not a great distance from my outspan, and rain have fallen from these storm-clouds; the reply is, for months prior to the rainy season commencing, clouds are formed after mid-day, and follow certain strata in the air, drawn by the electric condition of that portion of the earth's surface, and discharge the electricity they may contain without rain. I give this because I have on several occasions been stationary for some weeks in the line of country these clouds have taken, year after year, and at the same season. After the sun has passed the meridian, clouds have been collecting, generally from the north-east, and as evening advances, the vivid lightning and the heavy peals of thunder commence, and last for several hours, and then appear to evaporate, and a lovely starlight night succeeds; not a drop of rain has fallen during the storm, and a clear blue sky is seen over the whole of the horizon. In this part of the desert we are seldom below 3600 feet of sea-level, and, taking into consideration the clear and rarefied atmosphere, a flash of lightning and the thunder may be seen and heard at a greater distance than where the atmosphere is more dense. I may further observe, that owing to the rotundity of the earth, and the allowance to be made in every mile, it does not require that the clouds should be very far away to be partly below the horizon. When we place our eye on a level with the ground and look along a flat country, at ten miles' distance a man must be seventy feet high for his head to be seen above the horizon; therefore, at twenty or thirty miles, a portion of the clouds would be beneath the horizon, not a great distance for sound to be heard on a still evening, or a flash of light to be seen as evening closed in. These storm-clouds, without rain, always precede the rainy season, as also the sand-storms, and those gigantic whirlwinds that may be seen passing over the desert by the dozen, and extending in some instances 1000 feet high, carrying up sand, sticks, and other articles that lie in their course; many of them measure 100 feet through. It is a strange sight to see many of these sand-columns passing along over a plain. I have observed, where the first passes, in the course of the day others follow exactly in the same line: they indicate a change in the weather. The mirage is also of daily occurrence.