_Sandstone of Transition. Old Red Sandstone of Werner?_--Throughout the whole extent of the transition formation before mentioned, a sandstone occurs, evidently belonging to the oldest depositions of that rock. It is for the most part distinctly stratified, and in all cases its stratifications are inclined. It consists of grains of quartz, united by a scanty cement, and usually more or less rounded, as if by attrition and the operation of currents of water. Their fragments vary in magnitude from the finest sand to boulders of several pounds weight. Among the Alleghany mountains are many extensive beds of puddingstone or coarse conglomerate, usually coloured by oxide of iron. It is also to be observed, that this formation of transition sandstone sometimes embraces extensive beds, whose integrant particles have by no means the appearance of having been rounded by attrition. As in the case of almost all the rocks of secondary formation, there appear to have been periods during the time of its deposition when the waters of the superincumbent ocean ceased to throw down the mechanical _débris_ of former rocks, and deposited earthy matter from a state of chymical solution. It is perhaps one of the most interesting and most difficult problems which remain unsolved, to account for the alternation through the whole series of lower secondary and fletz rocks, of {329} beds of strata of mechanical with those of chymical deposition. The Alleghany mountains in New York, Pennsylvania, Maryland, and Virginia, are made up principally of rocks belonging to the transition class, and among these sandstone is perhaps of more frequent occurrence than any other aggregate. We are aware that Maclure has not considered the sandstones of the Alleghany mountains generally, as belonging to the old red sandstone formation of Werner; and it must be acknowledged there is some difference, at least in colour, between the ferruginous sand-rock, which commences on the shore of Tappan bay near Nyac, and extends south and west by the way of Newark, Amboy, and Brunswick, in New Jersey, and that which forms the body of the Cove, Sideling and Alleghany ridges farther to the west. But we cannot discover so marked a difference between the sandstone of the localities last mentioned, and that which occurs about the South mountain in Pennsylvania, that at Hagerstown in Maryland, and near Harper's ferry, in Virginia, which Maclure considers as the _old red sandstone_. Indeed, this last appears to us in almost every respect to resemble the inclined sandstone which prevails so generally throughout the middle and eastern ridges of the Alleghany mountains in Pennsylvania and Maryland. We have already stated the opinion, in part sanctioned by the observations of Maclure, that the old red sandstone is the great substratum of the part of the secondary formation south of Lake Ontario. If this be the case, what stratum, if not the old red sandstone, should be seen