The valley of the Nith, from the pass of Dalveen to Barjarg, incloses a space of nearly ten miles in length by four in breadth, filled with red sandstone and beds of limestone, and exhibits one of those original creeks or bays in the primary and silurian rocks which characterize this ancient belt. The lower basin, toward Dumfries and the Solway, presents the same series of extremely fine-grained strata. The small isolated basin of red sandstone near Lochmaben, and which contains the celebrated impressions of foot-marks in the beds at Corncockle Moor, as well as the very limited patch of sandstone in the vale of the Annan near Moffat, are probably referable to one and the same system with the above. And what is that system—the Devonian or Permian? The position of all these beds, and of others in Annandale, has long formed a fruitful subject of discussion with geologists and practical engineers, whether to regard them as an extension of the English new red, or to refer them to the predominant rock of the country. The latter view is borne out so far by the fact, that no borings, which have been both numerous and deep, have penetrated to the coal metals. On Greenough’s map, on the other hand, the former theory is adopted, where the coal-measures are represented as extending _underneath_ from Canobie, through Annandale to Arkit Muir, and as again emerging at Arbigland near Criffel. It has likewise been argued, that the foot-impressions on the slabs near Dumfries and at Corncockle Moor, have no analogues anywhere in the true old red of Scotland, while they are abundantly represented by the foot-prints of the newer sandstones of England and America. But now indeed such proofs are not wanting in America, that wide field of all organic things; the discovery has been made and assented to by the most competent authorities, that, in the old red sandstone of Pennsylvania, and 8,500 feet below the upper part of the coal formation, reptilian foot-prints are numerously and distinctly impressed, allied in form to the tread of the existing alligator. Then the larger orthoceræ and other testaceæ, found so plentifully in the limestones of Closeburn and Barjarg, also at Linburn and Shielgreen, would seem to claim very clearly and decidedly for the deposit in the middle basin of Nithsdale a Devonian origin.