One page Autograph Letter, signed. Approximately 7½x4¾". An additional clipped signature of James D. Dana is also included.

Dana writes an unknown recipient: "There is a chapter on Concretions in Prof. Hitchcok's Report in the Geol. of Mass., with many figures. But I know of no paper that discusses particularly their origin. I trusted in the subject in Vol. IV of the Journal near the close of a paper on Cohesion Attraction, but without a special reference to the facts or all the difficulties of the subject." James Dwight Dana (1813-1895) was the most eminent American geologist and mineralogist of the mid-19th century, a pioneering scientist who made ground-breaking studies of the structure of the world's continents and oceans, mountains and volcanoes - and correctly predicted the discovery of gold in northern California.