Sir Archibald Geikie corresponded with a number of people both socially and professionally. This sub-series includes the following correspondents:

There is a small amount of correspondence with FW Egan of the Geological Survey of Ireland. More lengthy professional correspondence with Geikie came from paleontologist Sir Philip De Malpas Egerton (1806-1881) concerning Sir Roderick Impey Murchison and letters of Murchison which Egerton lent Geikie. Another paleontologist, William Willoughby Cole, 3rd Earl of Enniskillen (1807-1886) wrote to Geikie concerning On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain, ( 1883).

Correspondence took place with the geologist and paleontologist Robert Etheridge (1819-1903) and a smaller amount with Etheridge's son, also Robert Etheridge (1846-1920), who was also a geologist and paleontologist. Geikie corresponded with archaeologist John Evans (1823-1908), Treasurer of the Royal Society, on a number of professional matters including those related to professional affiliations such as financial donations.