These letter books contain drafts or copies of Mayo's outgoing letters, bound in chronological order. The letters cover all aspects of Mayo's correspondence except official government despatches to the Secretary of State for India. The numbers against items in the list below are the folios on which they begin. Each entry gives the recipient of the letter, the place from which it was written, and date. Where no biographical details of a recipient can be provided, the place to which the letter is addressed is given, if available. Some letters received and memoranda are included in the letter books, and in these cases the author's name is also given. The books have indexes, created when they were bound, giving a summary of topics. Occasionally, letters have been bound in the wrong order.