The Red river of Louisiana enters the Mississippi from the west, in north latitude 31° 5´,[49] and in 16° 35´ west longitude from Philadelphia. From the Mississippi to the mouth of Black river (as the Washita is called below the confluence of the Ocatahoola and Tensa) is twenty-six miles by water. The aggregate width of Red river, for this distance, is from three hundred to three hundred and fifty yards. The depth of the water in summer varies, according to the actual measurement of Messrs. Freeman and Humphrey, from eighty-four to forty-two feet, the range from extreme high to low-water is from twenty-five to thirty feet, and the banks are elevated from fourteen to twenty-five feet above the surface of the river at low-water. At no great distance, on each side, is a second alluvial bank, rising a few feet higher than the immediate bank of the river. Back of this the surface is elevated nearly to high-water mark, but descends gradually towards the lakes and swamps, which occur along both sides of the valley of the river. In the wet season the lower part of Red and Black rivers are lost in an extensive lake, covering the country from the Mississippi westward near one hundred miles to the settlement of the Avoyelles.[50] The distinction made by Du Pratz, between the country on the south and that on the north side of Red river, appears to be strictly applicable only to {164} the part lying below the point where Red river enters the immediate valley of the Mississippi.[51] Above the confluence of Black river the bed of Red river immediately contracts to one hundred and twenty yards, which is its average width from this point to the rapids seventy-two miles above: the current becomes in a corresponding degree more rapid, running with a velocity of from two and a half to three miles per hour, at a moderate stage of water, in the early part of summer. The average depth in this section is stated at from eighteen to twenty feet, at a time when the water is twenty-one feet below its maximum of elevation. The banks are generally bold and steep on one side or the other, and often on both. The bottom lands are level and exceedingly fertile, but bear the marks of periodical inundation. The forests of the lower section of Red river differ little from those of the Mississippi and the Arkansa. White gum, cotton-wood, pecan, locusts, white oak, mulberry, sycamore, hackberry, and cypress occupy the low grounds, while the low and scattered hills are covered with pine, intermixed with a small proportion of oak and hickory. The only portion of the low lands in any sort fit for cultivation is a narrow strip immediately on each bank, commencing a little above the mouth of Black river, and enlarging upwards; but even here the settler is not secure, as uncommon swellings of the river sometimes lay the whole under water. Aside from this, the extreme insalubrity of the air, occasioned by the vicinity of extensive