These vast beds of sparry limestone, made up almost exclusively of deposits from chymical solution, would seem to have been formed during periods when great tranquillity prevailed in the waters of the primeval ocean; and their alternation with limestones of the common earthy variety, and with sandstones made up of fragments rounded by attrition, may be considered as proofs that those periods, whatever may have been their distinguishing peculiarity, alternated with other periods of a different character. This variety of limestone is perhaps the lowest rock hitherto noticed in the country of the lead-mines, and it may, according to the suggestion of Schoolcraft, be considered as the basis rock in that district; but as it certainly passes through every intermediate variety into the compact blue limestone, there seems to be no propriety in separating it from that rock, which often overlays the newest sandstones. If this view of the subject be admitted, it results that we are to consider {303} the whole of that part of the Ozark mountains which contains the lead-mines as belonging to a coal formation. We have met with nothing north of the Arkansa which appears to us to have any claim to be considered as belonging to the class of primitive rocks. Mr. Schoolcraft informs us, that granite, gneiss, and mica slate exist in Missouri, but has omitted to point out the particular localities. See Views of the Lead Mines, page 92. At St. Louis, Cote sans Dessein, Isle a Loutre, and at many points on the Missouri, the limestone partakes of the character of both the varieties above mentioned, but is rarely if ever so exclusively crystalline as in the lead-mine district. Most of the limestones between Franklin on the Missouri, and the Council bluffs, are distinctly crystalline, and are usually of a yellowish or reddish white colour. The horizontal limestone near the mouth of the Ohio, is of a bluish gray colour, of a compact or fine granular structure, and contains some metallic ores often occurring in veins of beautifully crystallized fluat of lime. Near some of these localities of fluat of lime, we have observed the rock itself to contain small and apparently water-worn masses of hornstone, and some fragments of a perfectly white granular limestone.