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“There is no safety but by flight.”

Mercury: or the secret and svvift messenger…
John Wilkins (1614-1672)
London: Printed by I. Norton, for Iohn Maynard, and Timothy Wilkins, and are to be sold at the George in Fleetstreet, neere Saint Dunstans Church, 1641
First edition
Z103 W68 1641

This codebook has charts and figures describing how the reader can master the art of secret communication. It is the first book in English on cryptology, published anonymously in 1641. John Wilkins, a chaplain who married Oliver Cromwell’s sister and became Bishop of Chester and a founder and first secretary of the Royal Society revealed himself to be the author when the second edition was printed that same year.

Mercury introduced the words “cryptographia” (secret writing), and “cryptologia” (secrecy in speech) into English. Wilkins defined “cryptomeneses” as the art of secret communication, in general. Wilkins described three kinds of geometrical cipher, a system in which a message is represented by dots, lines, or triangles.

The letters of the alphabet, in normal or mixed order, were written out at known spatial intervals, serving as the key. This line of letters was held at the top of a sheet of paper, and the message was spelled out by marking a dot for each plaintext letter underneath that letter in the key alphabet, each dot lower than its predecessor. The dots could then be connected by twos to form lines, by threes to form triangles, or all together to form what would look like a graph. Or, they could be left as dots. The receiver, who had an identically proportioned key, noted the positions of the dots, the ends of the lines, or the apexes of the triangles against the alphabetical scale to read the plaintext.

The end papers and flyleafs, front and back, are 17th century printer’s waste from an unidentified French to English dictionary. Ex libris Lawrence Strangman, a collector of 16th to 20th century English literature.