Accident threw in my way, on the 25th of August, a fact which led to the discovery of a primitive tract, on the southern borders of the mine country, the true geological relation of which to the surrounding secondary formations, formed at the outset rather a puzzle. I rode out on horseback on that day, with Mr. Stephen F. Austin, to Miller's, on the Mineral Fork, to observe a locality of manganese, and saw lying, near his mills, some large masses of red syenitic granite, which appeared to have been freshly blasted. He remarked that they were obtained on the St. Francis, and were found to be the best material at hand for millstones. On examination, the rock consisted almost exclusively of red feldspar and quartz. A little hornblende was present, but scarcely a trace of mica. This species of syenitic granite, large portions of which, viewed in the field, are complete syenite, and all of which is very barren of crystals, I have since found on the upper Mississippi, and throughout the northwestern regions above the secondary latitudes. The hint, however, was not lost. I took the first opportunity to visit the sources of the St. Francis: having obtained letters to a gentleman in that vicinity, I set out on horseback for that region, taking a stout pair of saddle-bags, to hold my collections. I passed through Murphy's and Cook's settlements, which are, at the present time, the central parts of St. Francis county. _Mine a la Motte_ afforded some new facts in its mineralogical features. I first saw this red syenite, in place, on Blackford's Fork. The westernmost limits of this ancient mine extends to within a mile or two of this primitive formation. The red clay formation extends to the granitic elevations, and conceals their junction with the newer rock. The nearest of the carboniferous series, in place, is on the banks of Rock Creek, at some miles' distance. It is there the crystalline sandstone. How far this primitive district of the St. Francis extends, has not been determined. The St. Francis and Grand rivers, both have their sources in it. It is probable the Ozaw Fork of the Merrimack comes from its western borders. Not less than twenty or thirty miles can be assigned for its north and south limits. The Iron mountain of Bellvieu is within it. The vicinity of the pass called the Narrows, appears to have been the locality of former volcanic action. A scene of ruder disruption, marked by the vast accumulation of broken rock, it would be difficult to find. Indeed the whole tract is one of high geological, as well as scenic interest. Had the observer of this scene been suddenly dropped down into one of the wildest, broken, primitive tracts of New England, or the north east angle of New York, he could not have found a field of higher physical attractions. Trap and greenstone constitute prominent tracts, and exist in the condition of dykes in the syenite, or feldspathique granite. I sought in vain for mica in the form of distinct plates. Some of the