James Campbell of Treesbank
Boswell was related to James Campbell of Treesbank by blood, James Campbell's mother being a Boswell, and by marriage, Boswell's wife being the sister of Campbell's second wife, Mary.
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On October 12, 1776, Boswell visited Campbell during his final illness and found him "much weaker and in a mild state of resignation, in so much that really the horror of his affliction, which I formerly could hardly bear, seemed now to be gone.". Boswell comforted him and prayed for him, making a fairly detailed note about the occasion in his journal.
Following the death in March 1777 of Campbell's widow, Mary, Boswell attended the funeral and afterwards
"searched poor Treesbank's cabinet, and took what letters related to Sir Walter's [...] affairs, or were written by my father or myself. It affected me with a strange feeling to observe how the most confidential papers of a dead man are ranscaked. I must really be cautious as to my own." 1
- 1. Journal entry for March 11, 1777.