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it in composition : thus, quartz-rock at Himmelsfiirst; a com pound of felspar and tourmaline at Marienbergh; porphyry at Halsbruck; hornblende-rock at Beschertgliick; and lime stone in numerous places. It also envelops granite in the form of irregular masses and veins, some of which are of con siderable size; and one mass, in particular, at Geyer, is well known in consequence of its having been extensively explored for tin ore, in which it abounds. The gneiss of Geyers- berg, which encloses this granite, is of the schistose variety, and composed of the common ingredients; the felspar, how ever, being in a less proportion than usual: its constituents are not indistinctly mixed together, but are individually ar ranged in small and undulating veins. The granite is fine grained, and formed of grey quartz, brownish mica, and red dish felspar, which is always the most abundant ingredient; it contains, here and there, a little indurated lithomarge, and shorl; is a very compact sonorous rock, capable of receiving a polish; occurs in beds of from two to ten feet in thickness, dipping 5° to 10° towards the south-east; and is traversed by numerous fissures, which intersect each other at various angles. Between this granite and gneiss there is always interposed a layer of some inches or feet in thickness, which is granitic, but very different from that just described. It contains fel spar and quartz in pieces of two to sixteen inches in length: the reddish felspar is still predominant in the mass; the mica is black in less proportion, sometimes in groups of two to six inches in size; and the quartz is often largely developed, crys talline, and compact, and in some parts in distinct pyramids, forming layers which alternate with others of indurated litho marge mixed with mica. Lastly, this variety of the granitic rock appears always to adhere both to the granite and the gneiss on either side: indeed, these granitic and schistose rocks are so intimately connected that they seem to belong to the same formation. The gneiss of the Erzgebirge generally passes into mica- slate ; so that it is often very difficult to distinguish the latter