[042] The Indiana coal fields are now known to embrace an area of about seven thousand square miles, chiefly in the southwest quarter of the state.--ED. {29} CHAPTER II The Ohio below the Rapids at Louisville--Ascent of the Mississippi from the mouth of the Ohio to St. Louis.[043] Our small boat descended over the rapids without injury; and having taken on board some wood near New Albany, we proceeded on our voyage, with a pressure of steam equalling one hundred pounds to the square inch, upon all parts of the engine exposed to its immediate operation. This enabled us to descend, at the rate of ten miles per hour. A small island in the Ohio, about twenty-three miles below the rapids, is called Flint Island, from the great numbers of fragments of flints, broken arrow points, and various instruments of stone, heretofore used by the Indians, which are found there on turning up the soil. This island has probably been the favourite residence of some tribe, particularly expert in the manufacture of those rude implements, with which the wants of the aboriginal Americans were supplied. The stone employed in these manufactures appears to have been, in most instances, that compact flint, which occurs in nodular masses, in the secondary limestones. In one instance we met with a triangular prism, of a very hard and compact aggregate of felspar, and hornblende, unlike any rock we have seen in the valley of the Mississippi. This prism was about five inches long, with faces of about {30} an inch in width, and was perforated, from end to end, forming a complete tube, with an orifice about half an inch in diameter, and smoothly polished, both within and without. We were never able to discover to what use this implement could have been applied; nor do we recollect to have met with accounts of any thing analogous to it, except, perhaps, those "tubes of a very hard stone" mentioned by the Jesuit Venegas, as used by the natives of California, in their treatment of the sick.[044] That it may have passed, by means of the intercourse of various tribes of Indians, from the primitive mountains of California to the rapids of the Ohio, is not, perhaps, improbable. Indirect methods of communication may have conveyed the productions of one part of the continent to another very remote from it. The savages of the Missouri receive an intoxicating bean from their neighbours on the south and west; these again must probably procure it from other tribes inhabiting, or occasionally visiting, the tropical regions. In the Philadelphia museum are many Indian pipes of that red indurated clay, found only (as far as hitherto known) on the Pipe Stone branch of the Little Sioux river of the Missouri; one of these, however, was found on the banks of the Rio de la Plata, in South America: several were found in the territory now called New England, and in the north-eastern part of the continent.