This is a facsimile copy of Alexander von Humboldt's letters to Bonpland (ca. 65 total), as well as Bonpland's botanical journal.

Correspondents include C. D. Ebeling, Alexander von Humboldt, and Henry Melchior Muhlenberg.

This microfilm contains correspondence from scientists, including Friedrich Wilhelm Bissell, 1816-1846 [from Deutsche Akademie der Wissenschaften, Berlin]; Matthew F. Maury, 1849-1859 [from National Archives, Washington, D.C.]; Paulus Usteri, 1789-1821 [from Bibliothèque Universitaire, Zurich; and Johann G. Galle, 1836-1858 [from Frau von Heinz, Schloss Tegal]. There is also correspondence from the Royal Society, London; Bibliothèque Nationale, Geneva; Göttingen University Library; British Museum; Massachusetts Historical Society; Bancroft Library of the University of California; Yale University; Henry E. Huntington Library; Library of Congress; the Alexander von Humboldt Kommission; Westdeutsche Bibliotek, Marburg; and Deutsche Staatsbibliotek, Berlin. The materials were, in general, collected by Helmut de Terra and contain correspondence with various scientists. A few items pertain to Humboldt's travels and general comments on American Indian linguistics.

Collection of 283 letters assembled and presented to the Academy of Natural Sciences of Philadelphia by John Torrey. Correspondents include: Louis Agassiz, Zaccheus Collins, Peter S. Du Ponceau, Elie M. Durand, Asa Gray, William Hembel, Alexander von Humboldt, William H. Keating, James Mease, Samuel G. Morton, George Ord, Charles Pickering, Constantine S. Rafinesque, Benjamin Silliman, Sr., John Torrey, Charles Waterton, Alexander Wilson.

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.

This collection is comprised of materials from seven repositories and includes correspondence from Banks' colleagues and explorers, such as John Hope, Josiah Wedgwood, Georg Forster, and Captain William Bligh; records of expenses for voyages and journeys; and journals kept during voyages to New Foundland and Labrador (1766) and around the world with Captain James Cook (1768-1771). Topics include botany and horticulture, marine life, and collecting specimens.

These are letters to Quetelet primarily on the subject of astronomy (meteorological observations), including charts showing directions of shooting stars.

The manuscripts of father William Mitchell and daughter Maria Mitchell are not easily separated, and are treated here together. The collection includes William Mitchell's autobiography, his memoir of Judge Walter Folger of Nantucket, astronomical and meteorological observations, lectures, family and other correspondence.