In concluding this narrative of facts, I should be glad to take a comprehensive view of the whole. The bold features in the geology of the United States, as they are drawn by the Blue Ridge, the Cumberland with its associated mountains, and the Dividing Ridge, deserve to be distinctly and strongly impressed upon the mind. Such is the order and regularity of their arrangement, that they can hardly fail to conduct the attentive observer to important results. What has now been said of them, is but an epitome of the whole. I trust the public will soon read, in the pages of your Journal, a detail more perfect and more interesting. And allow me to suggest, whether, under the auspices of our learned societies, some men of science might not be employed and supported in exploring the country, with the prospect of greatly enlarging the science of our country, and of enriching our Journals and Cabinets of Natural History. Tours of discovery have often been made for other objects, and with success. Our country yields to no other in the variety, or the value of its natural productions. We owe it to ourselves and to the world, to search them out with diligence and without delay. _Somers, (N. Y.) Oct. 1818._ ART. II. _On the Origin of Prairies._ _St. Louis, (Missouri Ter.) March 3, 1819._ SIR, The probable cause of the origin and continuance of _prairies_ has been the subject of much speculation among the learned and curious. The inquiry is interesting; and many theories have arisen; but although plausible and ingenious, they are, in my opinion, unfounded in fact. I should be glad to see the following remarks, which were called forth more particularly by the speculations of Caleb Atwater, Esq. (See No. 2. p. 116. of this work) appear in your valuable Journal of Science; and they are, for that purpose, at your service. With high respect, I am, Sir, your's, R. W. WELLS. _Benjamin Silliman, Esq._