Includes more than 12,000 letters and documents during the time of the Observatory's founder, Percival Lowell.

Most of this collection is original letters and drafts of Herschel's replies, with some miscellaneous papers other than letters. There are about 400 letters between Herschel and Charles Babbage.

This correspondence is primarily with George W. Corner, Executive Officer of the American Philosophical Society, concerning Whipple's membership in and contributions to the Magellanic Committee of the APS. This committee awards a medal for the best discovery in navigation, astronomy, or natural philosophy.

This item, by an unknown author, presents an astronomical sketch of eclipses, some of which could be seen from Philadelphia and Canton, China.

This essay formed the basis of lectures George Howard Darwin delivered before the Royal Institution of Great Britain on January 25, 1889. It was a popular account of a paper he read before the Royal Society the previous November ("On the Mechanical Conditions of a Swarm of Meteorites, and on Theories of Cosmogony," Proc. 45:3-16).

These volumes contain calculations and drawings of an eclipse of the sun, 24 June 1778, and of the moon, 29 May 1779, adjusted to the meridian of Philadelphia. There is also an incomplete duplicate of the calculations for the sun, and a duplicate of the calculations for the moon. An apparently personal reference in the text suggests that Freehauff was a native of Germany.

Included in these papers are letters, memoranda, computations, and tables.

These papers include letters from Admiral C.R. Moorson, correspondence with James Ross and Edward Sabine concerning polar exploration, and a map of the stars near the North Pole.

This is a small, miscellaneous collection of letters written to Alexander Brownlee, C. Scott, F. W. Surman, and Otto Zacharias. There are references to lunar tidal waves and mentions of Charles and Erasmus Darwin.

These letters are to William Hepworth Dixon, who was editor of the "Athenaeum," a journal of literature, science, the fine arts, music, and drama, from 1871 to 1900. They concern current publications and publishing expenses, Michael Faraday, astronomy, perspective, M. F. Maury, P. B. Du Chaillu, all in relation to the "Athenaeum" or letters to the editor thereof.

These papers include correspondence from over 180 individuals, lecture notes and essays on mathematics, astronomy, and electricity, and his diaries from journeys through Germany (1798) and Switzerland (1802).

This small volume records excerpts from British natural philosophy and scientific journals, written sometime after 1799. It covers a wide range of subjects, from astronomy to zoology.

The first volume contains mathematical problems, which appear to be college exercises (1814); the second volume is an essay on the projection of the sphere and spherical trigonometry, including an appendix on astronomy (1812); and the third volume is a lecture on natural philosophy, apparently prepared for delivery [n.d.].

This volume contains calculations of the distances of stars, eclipses, and longitude, made by William Maule, James Cresson, Joseph Jeanes, James James, and Robert Hutchinson, pupils in the Friends Academy, where Roberts was a teacher.

This account of Thomas Godfrey was prepared "with a view of having it inserted in Rees Cyclopedia," and is preceded by an essay concerning Godfrey and his quadrant taken from the "American Magazine" (1758). Also included in this volume is a copy of James Logan's communication to the Royal Society, and a letter from Spencer to Alexander Wilson, editor of the "Cyclopedia" (1809), which discusses Godfrey and the sources for this account.

This collection concerns astronomical observations, earthquakes, meteorology, photography, physics, professional associations, publications, and scientific instruments. The correspondents include Augustus De Morgan, Dionysius Lardner, Sir Francis Beaufort, and Sir Edward Ryan.

These classroom notes, taken by an unidentified student, present the state of knowledge in natural philosophy, especially astronomy, during these years. There are mentions of many contemporary scientists, and much on Newton and Newtonian philosophy.

This collection includes correspondence, notebooks, and memorandum books, lecture notes, published and miscellaneous papers, and academic and military records.