The first three volumes contain journals of Strahan's travels in Scotland, with records of expenses along the way, for 1751, 1759, 1760, 1766, 1768, 1773, and 1777. Strahan and Benjamin Franklin were in Edinburgh at the same time in 1759. The fourth volume contains "The particulars of the estate of Wm Strahan as it stood on the first of January 1755," and also for 1759 and 1761, with some miscellaneous accounts.

The first fifteen volumes of these "Notes of Travel" are Lea's account of his trips to Europe during 1832 and 1852-1853. He met with naturalists, scientists, and did much sightseeing in England, France, Germany, Italy, and Austria. He records in detail visits and discussions with scientists, and makes sketches of many of the places he saw, particularly the Rhine River. The sixteenth volume is a memorandum book, 1853, containing accounts and expenses while in Europe.

This collection contains minutes of the Society, 1781-1975; minutes of the directors of the Corporation, 1929-1947; membership book (with signatures of early members), 1785; and names of later members. There are also deeds to the meeting house and burying ground; treasurers' accounts; reports of officers and committees; bills and receipts for constructing, maintaining, and repairing the meeting house; cancelled checks; and letters to the Society and its officers, especially Samuel Wetherill, 1883-1884.

The papers include miscellaneous letters, letterbooks, books, certificates, and diplomas of various members of the Muhlenberg family. Among them are photostats of letters and papers of General John Peter Gabriel Muhlenberg and officers of the Continental Army on military affairs in the Southern Department during the American Revolution (1772-1804); photostats of letters to Albert Gallatin, Nathanael Greene, Edward Hand, Winthrop Sargent, Baron von Steuben, William Alexander, and George Washington; photostat of General Muhlenberg's journal of trips to the Ohio (1784, 1797); photostats of letters and notes of Gotthilf H. E. Muhlenberg, including a diary kept at Halle (1771) and extracts of thirty letters to Stephen Elliott of Beaufort and Charleston, South Carolina (1808-1815); photostats of letters of Henry A. Muhlenberg about his biography of General Muhlenberg (1848-1849); and photostats of letters of Henry Melchior Muhlenberg (1711-1787). Also included is an original letterbook of Peter Muhlenberg, paymaster of the United States Army, kept at Augusta and Savannah, Georgia (1836-1842). Henry Muhlenberg's notebooks (1784-1813), written in Latin or German script, in a small hand, includes a wealth of botanical observations, with a focus on Lancaster, Pennsylvania. The Henry Muhlenberg journals are a record of daily occurrences, with many features of a commonplace book, containing prescriptions, notes of questions asked candidates for the Lutheran ministry, and the plan of a barn. There is also a biographical account of Rev. Henry Melchior Muhlenberg (1711-1787).

In addition to family and business correspondence, the Charles Nicoll Bancker Family Papers contains various documents, such as a furniture inventory volume (30pp.); a Daybook, 1795-1800 (120pp.); and a very interesting journal (unidentified, but by one of the Banckers, and filed under "Description of a trip..."), from New York to Albany and back, between July 20-Aug. 15, 1793 (1 vol., 31 pp.). It contains detailed observations of the Hudson River and the towns along the way. Bancker was involved in business and trade prior to 1826, and in insurance after that date, so there is material relating to those topics in this collection. He owned a substantial library of the period, which was used by Charles Wilkes's Expedition after 1837 (see Reynell Coates to Bancker). This library, along with Bancker's notable scientific instrument collection, was sold after his death and there are published auction catalogues in the collection. There is much family correspondence from: Anne E. Bancker, Charles Gerard Bancker, Evert Bancker, Sarah U. Bancker, Violetta Bancker Talbot, Elizabeth Bancker Teackle, and John Teackle.