Captain Symmes published two other numbers at St. Louis, in the year 1818; the one went to prove, by geometrical principles, that matter must necessarily form itself into concentric spheres, and the other treated of geological principles. His two next numbers, marked four and five, (the one treating of the original formation of the Allegheny mountains, and the other claiming the discovery of open poles,) I have never had an opportunity of seeing. His sixth number appeared, dated at Cincinnati, in January, 1819, which contains a number of items and principles that he proposes treating of in subsequent numbers. His seventh number, entitled "_Arctic Memoir_," is dated at Cincinnati, in February, 1819; and another number, entitled "_Light between the Spheres_," dated at Cincinnati, in August, 1819, was published in the National Intelligencer. From that time to the present, numerous pieces from the pen of Captain Symmes have appeared in different newspapers; but the most prominent and grand doctrines, on which his theory is based, are contained in the papers above enumerated. Independent of his written publications, he has delivered a number of lectures on the theory,――first at Cincinnati, in 1820, and afterwards at Lexington and Frankfort, in Kentucky, and at Hamilton and Zanesville, in the state of Ohio. Several of these lectures I had the pleasure of hearing; and the respectable number of auditors, and the profound stillness that reigned, evinced in the strongest manner the interest felt by all present in the subject. In addition to the various facts and phenomena, to which he adverts in support of his positions, he delineates in his lectures, upon a wooden sphere, constructed on the principles of his theory, the cause of the winding meridians, the icy hoop or verge, and the course which ought to be pursued to reach the interior regions, with the confidence of mathematical certainty.