by a thin vapour which is spread over the ground in hot weather in India, but this appearance was entirely different, and on looking along the ground no vapour whatever could be perceived. The ground was quite level and smooth, and the weather very hot. It is only found in level, smooth, and dry places; the position of the sun, and the degree of heat, are not material, for it was afterwards seen in Damaun, when the weather was not hotter than in England." On the frontier of Caubul, Elphinstone saw what he calls a most magnificent mirage, {176} which looked like an extensive lake, or a very wide river. The water seemed clear and beautiful, and the figures of two gentlemen, who rode along it, were _reflected as distinctly as in real water_. "It is common in our own country," says the London Monthly Review, "for ground-mists to assume the appearance of water, to make a meadow seem inundated, and to change a valley into a lake; but these mists never reflect the surrounding trees and hills. Hence, the _mirage_ must consist of a peculiar gas, of which the particles are combined by a stronger attraction of cohesion than the vapours of real water; the _liquor silicum_ of the alchymists is described as exhibiting, in some circumstances, this glassy surface, yet as being equally evanescent."[125] It is afterwards suggested, in the same paper, that the gas which occasioned these extraordinary reflections, may probably be the substance of the pernicious wind called Simoom. The explanation here offered will not probably be thought satisfactory. It seems to belong to the epoch of great and brilliant discoveries in pneumatic chymistry, when "a peculiar gas" was thought the agent of every phenomenon. [124] Mission to Caubul, p. 179. 4to. Lond.—JAMES. _Comment by Ed._ Mountstuart Elphinstone (1779-1859), fourth son of the eleventh Baron Elphinstone of the Scottish peerage, was a notable official in the East Indian service, which he entered in 1796. In 1808 he was placed at the head of an embassy sent to Cabul to secure the alliance of the Afghans against a threatened French invasion. The work referred to, _An Account of the Kingdom of Cabul and its Dependencies in Persia and India_ (London, 1815), was one result of the mission. Elphinstone returned to England about 1830, declining the governor-generalship of India. [125] See Monthly Review for May 1817. p. 3.—JAMES. The images of pools of water, which we saw in the deserts of the Platte, appeared to us similar to those mentioned by Elphinstone, likewise to those observed by Nieburgh[126] in Arabia, where inverted images were seen.