This collection centers on Brown's geological investigations in various areas of Scotland and England concerning fossils, geological formations, deposits, etc. His activity in the Edinburgh Geological Society is documented in the letters and in newspaper clippings. Several of the letters contain diagrams, also geological maps (manuscript and printed) of Edinburgh and its environs, drawn by Charles Lapworth.

The collection is divided into two series. The first contains disparate letters from Airy relating to his publications and his position as Astronomer Royal of England, with mentions of topics such as: electrical experiments, magnets, Observatoire de Paris, stars, and telescopes. Correspondents in this series include: Edward Wedlake Brayley, James Challis, Alexander S. Herschel, Balfour Stewart, Septimus Tebay, John Washington. The second series features a group of documents put together by George May of the Harton Colliery at South Shields (1889) relating to Airy's pendulum experiments at Harton Pit in 1854 to measure the density of the earth.