source op st. peter's river.
199
it has been occasionally found in the conglomerate beds associated with this formation, particularly near Mendip-hills, in England; if it contains veins of sulphate of ba-rytes at the Huddleston quarry near Sherburn, between Ferrybridge and York; if it is traversed by veins of sulphate of barytes near Nottingham, at Bramham Moor, &c. may it not then be asked, whether these considerations do not render it probable that the great lead deposite of the west is in this limestone? and is it not likely that all that has been worked in an alluvion has been detached from this formation ? These are questions upon which, in the present state of our acquaintance with the western limestone, we must profess ourselves unable to give any decided opinion; but from various circumstances which we need not dwell upon, we should incline to consider the lead ore as probably existing in an older limestone whieh we think underlays this; and which may be connected with the mountain or carboniferous limestone of Messrs. Conybeare and Phillips, with the metalliferous limestone of other geologists.
The country becomes more undulated as we draw nearer to the Mississippi; the ridges are low but somewhat steep, owing to the horizontal stratification of the rocks; one of their sides very frequently discovers the composition of the hills by a steep break. At other times the country presents the waved appearance of a somewhat ruffled ocean; it is covered with a short dry grass, the vegetation generally appearing inferior to that of the alluvial country through which we had previously passed. This waved appearance seems to have been caused by the production of valleys subsequently formed, and extending from north-east to southwest, all dipping to the latter point; these are said to continue almost in a straight line to the Mississippi. Our object being to strike that river at a point further north, our