This collection of Morton letters forms part of a bound volume of incoming correspondence. It is a companion volume to the original letters in the Morton collection at the American Philosophical Society, which were also originally bound. Most of the subjects of the two collections overlap, but additional subjects in the microfilmed collection include American Indians, archaeology, Egyptology, and phrenology.

From negative microfilm held by Dr. Leonard G. Wilson, the collection consists mostly of incoming correspondence from English and American scientists, with a small section of correspondence from Lyell.

This collection includes letters to and from Americans (including South America and the West Indies) and letters about America selected from the Society's manuscripts (Classified Papers, Letter Books, Letters and Papers, Royal Society Letters, Miscellaneous Correspondence, and other official groups) and from collections of private papers (Sir Charles Blagden, William Buckland, John Canton, Sir John F. W. Herschel, Sir Edward Sabine, and others). The documents range in time and character from John Winthrop, Jr., "A Description of the Artifice & Making of Tarr & Pitch in New England" (1662), to letters from Sir Thomas Edward Thorne to his wife describing the American West, where he was on a surveying party in the 1880s.