The same conclusion as to the origin of the valleys may be reached in another way. Either the beds of rock were formed with their present topography, or the valleys have been excavated in them since they were formed. Their mode of origin will therefore help to decide between these alternatives. _Origin of the sandstone and limestone._--The sandstone of the region, known as the Potsdam sandstone, consists of medium sized grains of sand, cemented together by siliceous, ferruginous, or calcareous cement. If the cement were removed, the sandstone would be reduced to sand, in all respect similar to that accumulating along the shores of seas and lakes today. The surfaces of the separate layers of sandstone are often distinctly ripple-marked (Fig. 1, Pl. III), and the character of the markings is identical in all essential respects with the ripples which affect the surface of the sand along the shores of Devil's lake, or sandy beaches elsewhere, at the present time. These ripple marks on the surfaces of the sandstone layers must have originated while the sand was movable, and therefore before it was cemented into sandstone. In the beds of sandstone, fossils of marine animals are found. Shells, or casts of shells of various sorts are common, as are also the tracks and burrowings of animals which had no shells. Among these latter signs of life may be mentioned the borings of worms. These borings are not now always hollow, but their fillings are often so unlike the surrounding rock, that they are still clearly marked. These worm borings, like the ripple marks, show that the sand was once loose. The basal beds of the sandstone are often conglomeratic. The conglomeratic layers are made up of water-worn pieces of quartzite, Plate III, Fig. 2, ranging in size from small pebbles to large bowlders. The interstices of the coarse material are filled by sand, and the whole cemented into solid rock. The conglomeratic phase of the sandstone may be seen to advantage at Parfrey's glen (a, Plate XXXVII) and Dorward's glen, (b, same plate) on the East bluff of Devil's lake above the Cliff House, and at the Upper narrows of the Baraboo, near Ablemans. It is also visible at numerous other less accessible and less easily designated places. From these several facts, viz.: the horizontal strata, the ripple-marks on the surfaces of the layers, the fossils, the character of the sand, and the water-worn pebbles and bowlders of the basal conglomerate, positive conclusions concerning the origin of the formation may be drawn.