The mound builders of North America, north of the tropical latitudes, appear like bad copyists of a sublime original. They retained the idea of the oriental pyramid, but being no mechanics constructed piles of earth to answer the ancient purpose, both of worship and interment. Our largest structures of this kind, are the mound of Grave Creek in Western Virginia, containing about three millions of cubic feet, and the great group of the Monks of _La Trappe_ in Illinois, estimated at seven millions of cubic feet.[12] Those of Saint Louis, mount Joliet, and the Blue mounds respectively are now known to be of _geological_ origin. [12] The central mound of this group has been cut through since the date of my paper before the Ethnological Society, and proved to be _artificial_. But the Mexican and South American tribes built more boldly, and have left several specimens of the pyramids, which deserve to be mentioned, as well from the evidences they afford of mechanical skill, as from their magnificent proportions, and their Nilotic power of endurance. The pyramid of Cholula, in the valley of Mexico, exists in three vast steps, retreating as they ascend, the highest of which was crowned with a temple, whose base was one hundred and seventy-seven feet above the plain. This is nine feet higher than that of Myrcerinus, the third of the great group of Ghiza on the Nile; but its base of one thousand four hundred and twenty-three feet, exceeds that of any edifice of the kind found by travellers in the old world, and is double that of Cheops. To realize a clear idea of its magnitude, we may imagine a solid structure of earth, bricks and stone, which would fill the Washington parade ground, squared by its east and west lines, and rising seventy-five feet above the turrets of the New York University.