Deciphering the Hermeticae Philosophiae Medulla: Textual Cultures of Alchemical Secrecy.

This article presents the decryption, historical analysis, and alchemical interpretation of an alchemical cipher found in a shared notebook of John and Arthur Dee (British Library MS Sloane 1902). The cipher is an early example of a Bellaso/Della Porta/Vigenère type, a strong encryption method which was historically deemed indecipherable. The essay explores the medical and alchemical context for the manuscript into which the cipher was copied and provides the transcription, plaintext solution (in Latin), and English translation of the encrypted text. Further, it interprets the enciphered text through the lens of alchemical practice and provides evidence for the dissemination of this cipher as part of a larger alchemical knowledge network.