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The columns vary in the number of angles, from three, even to eleven or twelve; the medium polygons, from live to seven being prevalent, while, in the higher ones, the angular forms almost vanish. In all cases, the sides are in contact, or so little separated as barely to admit of the infiltration of carbonat of lime, if present; a striking point of difference, as formerly observed, between them and the prismatic bodies which result from the cracking of dried clay. No case of a single polygon thus aggregated has yet been observed; the various forms occurring together, and the adaptations being produced by the combination of many different prisms. The columns are sometimes continuous, at others jointed, obliquely or at right angles: being also ocasionally cracked, without the ap pearance of regular joints. These, when they exist, vary much in frequency; being sometimes repeated within the space of a few inches, at others, only after many yards. At times they are mere divisions, the surfaces above and below remaining flat; while, at others, they are irregularly undulated, and, more rarely, adapted by a mutual convexity and concavity ; the latter gene rally belonging to the lower surface. In a few rare instances, as in the Giants’ Causeway, each angle of the inferior joint is prolonged upwards into a denticle overlapping that of the superior one. Their sizes vary exceedingly, both with respect to length and dia meter: the longest which I know, in Sky, reaching to about 400 feet, and the shortest, in Morven, not ex ceeding an inch; while in diameter, those of Ailsa measure nine feet, and those of Morven, an inch, or less. Intermediate sizes are, of course, more prevalent. With respect to position, they are found placed in every manner, from the horizontal to the vertical angle, though attracting most attention in these latter cases, from their resemblance to the efforts of architecture