In this letter to Charles Thomson, he wrote "I purpose the following cypher...Use the second part of Boyer’s Dictionary where the English is placed before the French – it is not paged – you will therefore number the pages beginning with page – Letter A and so on regularly [when you work add five to the number of the page]. There are three columns – distinguish them – a under the first figures denotes the first, a under the second, the second, and a under the third, the third. Count the words from the bottom including the one you use and to the amount add 10…The dictionary I have is the thirteenth edition and was printed in London in the year 1771…"
Charles Thompson responded in 1780 (View Letter)
Charles Thomson to John Jay, 7 June 1780, John Jay Papers, Rare Book & Manuscript Library, Columbia University in the City of New York