Read it through once

At two o'clock the 'Susie' reached Troy, sixty-five miles above the mouth of Black River. Here on the left comes in Little River; just beyond that the Ouachita, and on the right the Tensas. These three rivers form the Black River. Troy, or a portion of it, is situated on and around three large Indian mounds, circular in shape, which rise above the present water about twelve feet. They are about one hundred and fifty feet in diameter, and are about two hundred yards apart. The houses are all built between these mounds, and hence are all flooded to a depth of eighteen inches on their floors.