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160 MICACEOUS SCHIST. deduced its relations to the primary strata: hut 1 must also add, that it is often immediately succeeded by the secondary, as in Cantyre. Micaceous schist, like all the primary strata, is dis posed in beds ; often, however, rendered obscure by their great thickness, by the want of distinct seams of division, and by the irregularities and contortions to which this rock is subject. When it enters in small quantity among other rocks, the beds are, how ever, always very distinct; and, in the Chlorite series, extremely regular and even. Its interior structure is various; sometimes consisting of straight laminae, rigidly parallel, and in one plane; while at others, the general parallelism of the laminae is maintained, but their thickness varies, so as to affect this appearance of regularity. In other cases again, these are minutely, or even largely undulated, still preserving the disposi tion in a plane; until, by at length increasing in size, they also lose that general conformity to an imaginary plane, finally assuming the most capricious contor tions; no longer bending round any given straight line or set of parallel lines, but presenting curvatures in every possible direction. From the frequent diffi culty of discovering the true position and limits’of the bed, it is thus sometimes impossible to know whether these curvatures involve the whole stratum, or whether they affect the interior structure only. The lesser un dulations and curvatures, are, evidently, often indepen dent of any corresponding change in the evenness of the bed ; and the same probably often holds true of the more complicated, since they do not seem to per vade the whole mass, but rather to occupy particular spots among the neighbouring and less disturbed la minae. In some of these cases, it is very difficult to trace the stratified disposition; and such a state of