Further illustration of this universal habit of mind may be gathered from even the smaller objects in nature. Children delight to recognise resemblances in things; the grown man learns to detect differences. Yet in regard to things that are unfamiliar, the man’s first instincts are those of the child. He seizes on the likeness which the newly observed objects bear to some already known to him, and he may even go so far as to mistake similarity for identity. Perhaps in no department of nature does this habit of mind manifest itself more flagrantly than in the mineral kingdom. People who know little or nothing of minerals or rocks, readily enough perceive a resemblance between some pieces of stone and certain plants, animals or inanimate objects, with which they at once compare or even identify them. In the vast majority of cases, there is no real connection between the stone and the object which it resembles. The likeness is merely accidental and external. Among the multitudinous shapes which concretions of mineral matter have assumed, a curious collection might be made of imitative forms. The ‘fairy stones’ of Scotland, found as concretions among deposits of clay, present endless rude figures of manikins, or portions of the human body, of fishes, birds, plants, cannon-balls, snuff-boxes, shoes, and innumerable familiar objects. Similar concretions occur all over the world, and have long attracted popular notice. [Sidenote: SUPPOSED ANIMAL FOOTPRINTS] An Orkney laird once wrote to me that his people, while removing flagstones from the shore of his island, had made an extraordinary discovery, no less than ‘the footprints of men, women, children and animals,’ all impressed on the solid stone and in excellent preservation, and he courteously offered to send me some specimens of these interesting remains. The identification of the impressions as human relics was of course out of the question, for the rock that contained them belonged to the Old Red Sandstone, which was deposited long before any trace of man appeared upon the earth. Nevertheless, as there was just a possibility that among the specimens, there might be some new fossils, which might add to our knowledge of the flora or fauna of that ancient formation, I asked the proprietor to be good enough to send a few examples of the ‘find.’ In due course one or two large boxes arrived containing several hundredweight of stone. But every one of the specimens was merely the cast of a mineral concretion. Yet they were curiously like footprints. One looked as if a young man, in going out to a ball, had stepped with his dress-boot upon soft mud, into which he had sunk about an inch. Another seemed as if it might have been made by a rough-shod farmer, springing from his dog-cart upon the surface of a muddy pool. There were prints resembling misshapen female feet, and one or two might, with a little imagination, have been taken for prints of infants, whose fond mothers were trying