A British Book Cipher during the American Revolutionary War

During the American Revolutionary war, a book cipher was used between Frederick Haldimand, Governor in Quebec, and Sir Henry Clinton, Commander-in-Chief in New York. It is described in a new article, "Haldimand-Clinton Book Cipher (1778-1782)".

It appears that the book cipher was also applied in letters from Lord Germain. It is wondered whether ciphers had not been used in trans-Atlantic communication. British ciphers during the Revolutionary War are also outlined.