The Letter Books contain copies of outgoing correspondence from the Secretary to missionaries (mainly the mission secretary).

Letters to the Bishop of Calcutta, Rev J Innes, Rev J F Osborne and Rev S Hasell. There are instructions to new missionaries such as Rev E Johnson, Rev R M Lamb advising them to acquire the native language as soon as possible. Included also are discussions re conferences to be held and travelling allowances to be paid to missionaries.