In the space of one hundred and seventy-six years the Mississippi has shortened itself two hundred and forty-two miles. Therefore, in the Old Silurian Period the Mississippi River was upward of one million three hundred thousand miles long, seven hundred and forty-two years from now the Mississippi will be only a mile and three-quarters long. There is something fascinating about science. One gets such wholesome returns of conjecture out of such a trifling investment of fact.