This is a small group of letters written to Johann Ambrosius Beurer, J. von Sprehelson, and Christoph Jacob Trew.

These letters concern various scientific subjects, such as fishes, insects, snakes, mice, fossils, and mosses. Other subjects include learned institutions, notably the Smithsonian Institution and the Academy of Natural Sciences of Philadelphia, and men of science. Correspondents include S. S. Haldeman, Walter J. Hoffman, Spencer F. Baird, Edward D. Cope, and Leo Lesquereux.

Correspondence compiled by Edward E. Wildman and Francis D. West, chiefly from original letters in the Historical Society of Pennsylvania and other depositories, 1956.

Nine of these letters are addressed to Sir Alexander Dick of Edinburgh (1763-1768), and relate to Morgan's medical studies, his travels on the Continent, and the founding of the medical department of the College of Physicians. These are copies of originals in possession of Mrs. Dick Cunyngham, Prestonfield House, Edinburgh. In addition there are letters from Morgan to: Petrus Camper, William Smith, Samuel Vaughan, Jr.; and from Peter Collinson to Camper; Camper to Morgan; S. Vaughan Jr. to Camper; and an exchange between Christian F. Michaelis and Camper. These concern Morgan, with mentions of fossils (mastodon bones in America), natural history, comments on Franklin, Jefferson, and Angelica Kauffmann. These are from originals in the Petrus Camper Papers, on deposit (1976) at the University of Amsterdam Library.

Benjamin Silliman (1779-1864, APS 1805) was a scientist and educator. As a professor of chemistry at Yale University from 1802 to 1853, and pioneering teacher of chemistry, mineralogy and geology, Silliman was largely responsible for the conversion of Yale College to Yale University, with strong medical and scientific departments.

These papers include letters on natural history, metals and mineralogy, botany, insects, the geological survey of New York, and analyses of distilled liquors in the cause of temperance.

Principal correspondents in the lettes of John Fries Frazer include Alexander Dallas Bache, Louis Agassiz, Joseph Henry, and Titian Ramsay Peale who discuss mainly general scientific topics, although personal and family matters are discussed with Bache. Topics include the University of Pennsylvania, boiler explosions, chemistry, education, the National Academy of Sciences, the Smithsonian Institution, fossils, magnetism, solar eclipses, the American Philosophical Society, weights and measures, the U.S. Coast and Geodetic Survey, scientific instruments, the American Civil War, electricity, the United States Mint, the Franklin Institute, scientists of the period, natural history, and publications.

This is a small but diverse collection documenting Wheatley's interests in mines and mining technology, paleontology, mineralogy, and shells. There are sketches of Wheatley's mine near Phoenixville, Pennsylvania; estimates of costs of machinery, and a list of furnace products sent to the Centennial Exposition.

This collection includes letters from, and drafts of letters to, scientists, artists, musicians, soldiers, political figures, and court personages throughout Europe, especially Italy and France. Topics covered range from personal and social affairs to agriculture, botany, geology, natural history, coinage, museum management, politics, weights and measures, current affairs. The collection also includes four diaries, housed separately with manuscript volumes.