The fonds documents A.D. Blackader's personal and professional life. The fonds contains correspondence, diaries, autobiographical notes, papers and lectures, certificates, diplomas, testimonials, article reprints, photographs, and some memorabilia.

Very few of the McLeod papers actually concern the Observatory. However, his work for the railways and in Newfoundland is documented, as are his views on the education and employment of engineers. The basic record for the early part of his career is a diary kept from 1870 to 1875, regarding student days and early work on the Observatory. An essay, "Winter under canvas" (1868) describes an early surveying job, and a letter from his father (1872) inquires about his academic progress. His work for the railways is documented by three letters of recommendation, and two letters (one from Stanford Fleming) on the work of his colleagues in the West. The Newfoundland survey (1875) is described in McLeod's diary, a manuscript essay "Across Newfoundland" (1876), his printed reports and three letters. His work at McGill is represented by six letters (largely official acknowledgements of appointments), and McLeod's manuscript notes on McGill history. McLeod's concern with the engineering profession is reflected in two addresses on education and professional development, and copies of about a dozen letters to Sir Wilfrid Laurier (1906-1908), C.A. McGrath and E.F. Wurtele (1912), largely on the employment of engineers in the civil service.