Note 368 — Chapter XVIII
Reading edition
The Mississippi is continually shifting its course in the great alluvial plain, cutting frequently to the depth of 100, and even sometimes to the depth of 250 feet. As the old channels become afterwards filled up, or in a great degree obliterated, this excavation alone must have given a considerable depth to the basin, which receives the alluvial deposit, and subsidences like those accompanying the earthquake of New Madrid in 1811-12 may have given still more depth.