I have recd. your favor of May 20. with the 2 printed papers: one on the “Tertiary formations,” the other on the “Celtic Antiquities of America”; for which I return my thanks.

Without venturing to decide on the validity of these ingenious Speculations, I may express my respect for the philosophic & literary character of which they bear the stamp. They merit each of them the further researches requisite in such cases. The second involves the question how far similar monuments, of the simplest forms and the most obvious materials, among different communities, in their rudest stages, may be derived by either from the other, or be a spontaneous result of propensities & situations common to both. I offer you Sir my respects & good wishes