The course of the river, below the Falls of Pakagama, is still serpentine, but strikingly less so than above, and its bends are not so short and abrupt. The general course of this river, till it reaches the rock formation of Pakagama, is from the west. Thence, to Sandy Lake inlet, it flows generally southeast; from this point to the inlet of the De Corbeau or Crow Wing, it is deflected to the southwest; thence almost due south, to the mouth of the Watab River; and thence again southeast to the Falls of St. Anthony. A geographical line dropped from the inlet of Sandy Lake, where the channel is first deflected to the southwest, to St. Anthony's Falls, or the mouth of the St. Peter's,[77] forms a vast bow-shaped area of prairie and forest lands of high agricultural capabilities, whose future products must be carried to a market through the Fond du Lac of Lake Superior. These prairies and grove lands, which cannot square less than two by four hundred miles, constitute the ancient area of the Issati,[78] and are now the resort of great herds of the buffalo, elk, and deer; and it is a region known as the predatory border, or battle-ground of the Chippewas and Dacotas. [77] Now called Minnesota River. [78] _Vide_ Hennepin. CHAPTER XI. Physical traits of the Mississippi--The elevation of its sources--Its velocity and mean descent--Etymology of the name Mississippi--Descent of the river to Sandy Lake, and thence to the Falls of St. Anthony--Recross the great Bitobi Savanna--Pakagama formation--Description of the voyage from Sandy Lake to Pine River--Brief notices of the natural history. The third geographical division in which it is proposed to consider the Mississippi, begins at the Falls of St. Anthony. Within half a day's march, before reaching this point from its sources, the primitive and crystallized, and the altered and basaltic rocks are succeeded by the great limestone and sandstone horizontal series of the carboniferous, magnesian, and metalliferous rocks, which constitute by themselves so extraordinary a body of geological phenomena. Entering on the level of the white sandstone stratum, which is fundamental in this column, about the inlet of Rum River, the Mississippi urges its way over a gently inclining bed of this rock, to the brink of this cataract, where it drops perpendicularly about sixteen feet; but the whole descent of its level from the head to the foot of the portage path, cannot be less than double that height.