[219] In 1825, Lieutenant Charles F. Morton, U. S. A., sent to my office a mass of this red sand rock, of about twelve inches diameter, perfectly round and ball-shaped, which he had directed one of the soldiers to pick up, in an excursion among the islands of the lower St. Mary's. This ball was a monument of that physical throe which had originally carried this river through the sandstone pass of St. Mary's, having been manifestly rounded in what geologists have called "a pocket hole" in the rock at the falls, and afterwards carried away, with the disrupted rocks, down the valley. [220] The Indiana call it _Pauwateeg_ (water leaping on the rocks), when speaking of the phenomenon, and _Pawating_, when referring to the place of it. RED SANDSTONE OF LAKE SUPERIOR.--That this is the old red sandstone, may be inferred simply from the fact that, although deposited originally in horizontal beds, its position has been disturbed in many localities. PLASTIC CLAY STRATUM OF THE LAKES.--The northern extremity of Muddy Lake--a sheet of water some twenty miles in length--is the head of the straits, and the beginning of the River St. Mary's. This sheet of water has the property of being rendered slightly whitish, or turbid, by continuous winds. Its bottom appears to be formed of the same plastic blue clay which obstructs the passage of vessels of large draft on the St. Clair flats, and forms an impediment of a similar kind in this river in Lake George. This stratum seems to be the result of causes not now in operation. If dredged through, or excavated, there is no reason to suppose it would again accumulate; for the waters of the lake are clear and pure, and carry down no deposit of the kind. These clay deposits remain to attest physical changes which are past. They denote the demolition of formations of slate in the upper regions, which have been broken down and washed away when the dominion of the waters was far more potential than they now are. This formation is favorable to the growth of some species of fresh-water shells. I observed several species of the anadonta and the plenorbis, and think, from the broken valves, that research would develop others. PORPHYRY AND CONGLOMERATE BOULDERS.--A formation of red jasper, in common white quartz, exists, in the bed of intersection, on the southeastern foot of Sugar Island. The fragments of jasper are of a bright vermil red, quite opaque, and have preserved their angles. I had observed fragments of the formation along the shores of the lower part of the straits, and even picked up some specimens, entirely abraded, however, on the south shores of the Huron, between the White Rock and Michilimackinac--a proof of the course of the drift.