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

Joseph Wilson Lowry (1803-1879) was engraver to the British Geological Survey and wrote to Geikie in this context.

Sir John William Lubbock (1834-1913) wrote regarding social arrangements, introducing colleagues, and a joint venture amongst various professional associations.

Katherine Murray Lyell (1817-1915) wrote regarding her brother-in-law, Sir Charles Lyell (1797-1875), and her son, Sir Leonard Lyell (1850-1926) wrote regarding his maternal grandfather, Leonard Horner (1785-1864).

Sir Henry George Lyons (1864-1944) organized the Geological Survey of Egypt and wrote to Geikie about his work there, including seeking advice on methods used in Britain.

Alexander Macbride (1807-1875) was the Free Church minister for North Bute. He wrote to Geikie on a number of matters.

Alexander McHenry (fl1881-1894) worked for the Geological Survey of Ireland and wrote to Geikie concerning the work he was doing there, maps, and discussion around the 'Torridon Rocks'.

Sir Andrew Douglas Maclagan (1812-1900) sent Geikie some siliceous concretious samples.

Charles Maclaren (1782-1866) was first editor of the Scotsman and had a strong interest in geology. He arranged several meetings of a social nature with Geikie. His letters also include an 1839 letter to Sir Charles Lyell on his own geological research and seeking an opinion on his publication, most likely A sketch of the geology of Fife and the Lothians : including detailed descriptions of Arthur's Seat and Pentland Hills, ( 1839) .

Robert Mallet (1810-1881) wrote regarding tide levels and various types of geological formations.