This series of correspondence is arranged alphabetically, A-Z, including one ‘Miscellaneous’ section within the 'M' series. Each correspondent has been assigned a file number – there may be several folders within that file, evidencing the longevity and depth of the relationship between Lyell and the correspondent - for example his brother in law Charles Bunbury.
Lyell himself, Mary or Arabella Buckley have mostly recorded a summary of the contents of the correspondence, either on the letter itself, or, on the associated envelope. These summaries have been used as the basis of the catalogue description.
There is a second series of A-Z correspondence within the second tranche, reference Coll-203/B1; these two collections will have been originally together. Other correspondence, also showing evidence of the same summarising found in this series, has been lifted out, and used to populate albums, created by Lyell's nephew Leonard, see Coll-1997/1 and 2.