In the wide space included within the lines above mentioned, we know of but one exception to the remark, that all the rocks found in place are secondary. This is the instance of the Ozark hills traversing the horizontal strata from south-west to north-east, somewhat in the manner of a whindyke. The most striking peculiarity of this range, is the prevalence among the secondary strata of crystalline substances, and what are called rocks of chymical deposition, and the alternation of these with beds and strata whose integrant particles bear evident marks of having been worn and rounded by mechanical attrition. {319} Appearances of this kind are observed in all formations of secondary rocks, but it is believed, are, in few instances, as extensive or as numerous as in this. It is well known, that the ores of lead, so abundant in many parts of this range, occur in the uppermost strata of horizontal sandstone, or in primary soils superimposed upon those sandstones. It has been suggested, that these ores of lead may have been brought down in the alluvion of rivers from some more ancient and elevated region, but any one who shall examine them in connection with the substances with which they are now found associated, will, we think, be convinced of their having been of contemporaneous origin with the sandstone. That the sparry limestones, the crystalline sandstones, and perhaps the ores of lead, (almost invariably found in the form of crystals,) have been deposited from solution in water, is highly probable; and that these depositions must have taken place in connection with circumstances not unfavourable to animal life is evident, as all these crystalline rocks abound in organised remains. In attempting an explanation of these appearances, can any assistance be derived from recourse to the ingenious suggestion of Bakewell, that _the matter of these crystalline beds and strata has been ejected from beneath the crust of the earth in a state of chymical solution_. These submarine eruptions may have been numerous, and may have happened at different and remote periods; hence the alternation of rocks, consisting of particles mechanically aggregated together with those of chymical deposition. Hence the existence of metallic ores overlaying recent marine sandstones and compact limestones; for these ores, in a state of solution, may have been the matter thrown out in some of the latest eruptions.