{45} Compact and sparry limestones are frequent in this region; but all the rocks seem to be acted upon with great rapidity by currents of water. The country on the east side of the Mississippi, back of Fort Chartres, and about the river St. Mary, is much broken by sink holes, having the form of a funnel, and occasioned, probably, by the action of subterraneous streams of water finding their way through the friable sandstones, which underlay the deep and fertile soils in those places. We passed in succession the mouths of the river St. Mary, opposite to which is the fine settlement of the Bois Broule bottoms; the Ocoa, or Kaskaskia river; the St. Lora, a handsome stream, from the west; and the Gabaree Creek, on which stands the old French town of St. Genevieve.[065] The navigation of the Mississippi, above the mouth of the Ohio, is at all times difficult. The current is considerably accelerated by the descent of the river over the rocky traverses which cross its bed. At times of low water, innumerable sand-bars occur in various parts of the channel, rendering the navigation extremely precarious. A little below the mouth of the Kaskaskia, is a creek called the Saline, entering on the west side. A grant of a tract of land, one league square, was here made by the Spanish government, in favour of a Frenchman named Pegreau, the founder of the deserted town called New Bourbon.[066] The tract included a valuable brine spring, near the mouth of the creek. The proprietor built a house near the bank of the Mississippi, where he resided for some time, and carried on a manufacture of salt; but having occasion to go to France, he rented his works to a man, who for want of funds, or for some other reason, failed to keep them in operation. After the transfer of Louisiana to the United States' Government, this grant, among others, became an object of speculation; and advantage being taken of Pegreau's absence, the worthless tenant was instigated {46} to prosecute his landlord for breach of contract, and by a legal process recovered damages to the amount of nine thousand dollars, for the disbursement of which the property was sold, and fell into the hands of the present proprietors. At the mouth of the Kaskaskia river, on the east bank of the Mississippi, a town has been recently commenced, called Portland. The high lands approach here to the brink of the river, affording an elevated and advantageous site. The landing is said to be good; and there is reason to expect that Portland will soon rival the old town of Kaskaskia, the present seat of a great portion of the mercantile business in this part of Illinois.[067]