The small but rich collection of Slessor correspondence in Dundee City Archives, consisting mainly of Mary's warm communication with Miss Crawford, (an administrator and friend in the Free Church of Scotland), complements the larger collection held in Dundee Central Library of her letters to Partridge, a colonial administrator. A descendant of Miss Crawford's family in Aberdeen generously decided to place the letters in Dundee City Archives for safe keeping in 1993 but their comparatively recent discovery means that their existence is not widely known.

Mary's humour is evident from her first manuscript letter of 1901, in which, having been asked for her date of birth for annuity purposes, she states that the document giving the year has been eaten by ants, but that she hopes to escape all obligations to any annuity fund by being able to 'hold her small fort to the last stage of the Pilgrimage'. These were prophetic words, for Mary's unfailingly cheerful correspondence with both Crawford and Partridge were to continue, despite illness, delay and frustrations, until shortly before her death in harness in 1915. Her last letter, in December 1914, to Miss Crawford - by then her 'very dear friend'- is littered with scriptural references, and combines testimony to her faith with concern about conditions in the trenches in Europe, references to the war in Cameroon, and the statement that she is sending her requests via the 'heavenly wireless'.

Another complementary factor in Mary's two series of correspondence with the two administrators - one colonial, one ecclesiastical - shows the ease with which she dealt with all levels of people, and the eye that she had for detail. Her writing might be hurried and her expression hampered by a lack of formal education, but she consistently shows herself to be a highly competent and intelligent administrator with clear objectives. The Crawford collection is rounded off by a number of miscellaneous prints of articles which clearly indicate contemporary interest in her activities, trials and successes.