[Vols. I & II] During the First Thirteen Centuries of our Era; [Vols. III & IV] Fourteenth and Fifteenth Centuries; [Vols. V & VI] The Sixteenth Century; [Vol. VII & VIII] The Seventeenth Century.
Although dated as first published, all these volumes are numbered as later impressions (I & II seventh; III - VI sixth; VII & VIII fifth), and all have 10-digit ISBNs, and so were printed sometime between 1970 and 2007. For a work commenced by the author in 1902, this continuity in print is testament indeed to the durability of scholarship and application.