Douglas wrote: •
A General Essay on Military Tactics; with an introductory Discourse, translated from the French of
Jacques Antoine Hippolyte, Comte de Guibert, 2 vols. Lond. 1781. •
Travelling Anecdotes, through various parts of Europe, vol. i. (all published), Rochester, 1782 (anon.); 2nd edit. with the author's name, Lond. 1785; 3rd edit., Lond., 1786. Influenced by
Laurence Sterne, with plates drawn and etched by the author. •
A Dissertation on the Antiquity of the Earth, Lond. 1785. •
Two Dissertations on the Brass Instruments called Celts, and other Arms used by the Antients, found in this Island, with two
aquatint engravings. It formed No. 33 of the
Bibliotheca Topographica Britannica, vol. i. 1785. •
Nenia Britannica, or a Sepulchral History of Great Britain, from the earliest period to its general conversion to Christianity, Lond. 1793, dedicated to the Prince of Wales. Published in numbers (1786–93) at 5s. each. It contains a description of British, Roman, and Saxon sepulchral rites and ceremonies, and also of the contents of several hundred ancient places of interment opened under the inspection of the author, with added observations on Celtic, British, Roman, and Danish
barrows discovered in Great Britain. The tombs, with all their contents, are represented in aquatint plates executed by Douglas. Objects found by Douglas in his excavations and engraved in this work were sold by his widow to
Sir Richard Colt Hoare, who in 1829 presented them to the
Ashmolean Museum at Oxford. •
On the Urbs Rutupiæ of Ptolemy, and the Limden-pic of the Saxons, in vol. i. of
Bibliotheca Topographica Britannica, 1787. •
Discourses on the Influence of the Christian Religion on Civil Society, Lond. 1792. Douglas painted portraits of his friends, both in oil and in miniature. In 1795 he contributed to
John Nichols's
Leicestershire a plate of
St Michael's Church, Coston engraved by himself. He also engraved the full-length portrait of
Francis Grose. ==Family==