Contains letters and copies of letters on botanical subjects, principally algae, many on the identification of species and on the sale and exchange of mounted specimens. 18 items refer to the United States Exploring Expedition (1838-1842).

The youngest son of Charles Willson Peale, Titian Ramsay Peale was an accomplished artist, naturalist, and explorer. This collection of ink, pencil, and watercolor sketches, with some engravings and lithographs, forms the bulk of Peale's artistic output. The drawings can be grouped into several periods of artistic output: pre-1818 (primarily watercolors of butterflies); from the Stephen Harriman Long Expedition to the American west in 1819-1820, on which Peale traveled as zoologist (there are views of animals, Indians, landscapes, etc.); for his 1821-1838 interlude period, spent primarily on the east coast (insects, animals, moose hunting in Marine, his trip to South America in 1830-1831, coin and medal designs); his period as a naturalist on the worldwide U.S. Exploring Expedition under the command of Charles Wilkes, 1838-1842; from the 1849-1873 period when he sketched around Washington, D. C. and in New Jersey; and there are more than 160 undated sketches of: animal skulls and bones, birds, plants, fish, insects, landscapes, and zoology.

Through his craniometic studies of human races, the Philadelphia physician Samuel George Morton (1799-1851) exerted a profound influence on the development of physical anthropology in antebellum America, and made substantial contributions to mineralogy, paleontology, and natural history. Relating primarily to Morton's scientific interests, the Morton Papers include insights into Morton's perspectives on education, medical practice, geology and mineralogy, craniology, paleontology, the Wilkes Exploring Expedition (also known as the United States Exploring Expedition 1838-1842), and his two major monographs, the Crania Americana and Crania Aegyptiaca. Several of the letters were written by Morton in his capacity as corresponding secretary of the Academy of Natural Sciences of Philadelphia. Also included in this collection are Morton's "Some Remarks on the Infrequency of Mixed Offspring Between the European and Australian Races" (1850), Joseph Barclay Pentland's notes on the aborigines of Peru (ca. 1840?), and newspaper clippings on Morton's death; a diary of Morton's trip to the West Indies, 1834, a set of craniological sketches for use in Crania Americana, and a microfilm of letters in private hands, written to Morton, 1838-1844

Though the Miscellaneous Manuscripts collection is composed of items that do not fall readily into any other existing collection, the two dominant intellectual areas represented in the collection are Early American History and History of Science.

George Ord made important contributions as an ornithologist and writer but is also famous for his contempt of fellow ornithologist John James Audubon. Throughout his life he published numerous scientific articles and assisted in completing Alexander Wilson's life's work, American Ornithology; or, The Natural History of the Birds of the United States. Ord also left his mark as a member of the American Philosophical Society and as the president of the Academy of Natural Science of Philadelphia. The George Ord collection consists primarily of outgoing personal correspondence to Charles Waterton ranging from 1831 to 1866 that highlights Ord's professional as well as personal affairs, most notably his hostility toward Audubon. The collection is supplemented by correspondence of Ord's to and from various individuals regarding personal and business matters.