The Mural Diagraph, or the Art of Conversing Through a Wall de Swaim, James - 1829

Philadelphia: Printed by Clark & Raser, 1829. 18 mo. 13 x 70 mm., (5 1/4 x 2 3/4 inches), 24 pp. Contemporary calf leather spine over marbled paper boards. Each leaf is interleaved with a blank for notes and additions. This work described the process of rapping, a way of communicating through walls or in places where verbal communication is not possible. The system uses a numerical code to create equivalents for letters and phrases. It is a form of early information theory, and a forerunner of more complicated digital codes that were to become the foundation of modern computation. The act of 'rapping' as a method of conveying non-verbal communication can also be viewed as a form of 'cryptography', where messages are reduced to a numerical code understood only by someone who was privy to the code sequence. James Swaim was the son of William Swaim of "Patent Medicine" fame. One wonders if the publication of this little guide to 'rapping' may not in itself be a code for mediums to communicate with the spiritual world, an activity that has credence in early 19th century America. American Imprints 40580. NUC cites copies at Columbia and the Free Library of Philadelphia. OCLC only cites two copies at the British Library.