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EXPEDITION   TO   TIIJS
connected with the view of a primitive formation which we had not seen since the first five days of our journey; but it resulted also in a great measure from the certainty that we had at last arrived at what we had long been looking for in vain. We had traced those scattering boulders, which lay insulated in the prairies, from the banks of the Muskingum to this place. We had seen them gradually increasing in size and number, and presenting fewer signs of attrition, as we advanced further on our journey. Two days before, their number, size, and features, had induced the geologist of the party to predict our speedy approach to the primitive formations, and it was a pleasing confirmation of his opinions to find that these rocks had really been seen in situ, within thirty miles, in a straight line, of the place where he had made this assertion. The character of these rocks was examined with care, and found very curious. It seemed as if four simple minerals, quartz, feldspar, mica, and amphibole, had united here to produce almost all the varieties of combination which can arise from the association of two or more of these minerals; and these combinations were in such immediate contact, that the same fragment might, as we viewed one or the other end of it, be referred to different rocks; while in some places granite was seen perfectly well characterized, varying from the fine to the coarse-grained; in others, a gneiss, mica slate, greisen, (quartz and mica,) compact feldspar, (Weisstein of Werner,) sienite, greenstone, and the sienite with addition of quartz, forming the amphibolic granite of D'Aubuisson, were equally well characterized. The only rock composed by the union of two of these principles which we did not observe, but which may perhaps exist there, is the graphic granite, (Pegmatite, Hauy.) These rocks are not very extensive; the circumference