of the History of Computing. v.3. n.3 (July 1981): 226.) Finally, a U.S. Army document describing the Polish Bombes claims, "When a possible solution was reached a part would fall off the machine onto the floor with a loud noise. Hence the name 'bombe"." (6812th, 10.)

5. Traffic analysts look at information outside of the actual message text such as the unenciphered headers prior to the message, time of transmission, and the frequency used. With this type of information, traffic analysts can reconstruct an enemy's communication network and hierarchy.

6. Britain called their sheets "Jeffreys sheets" after John Jeffrey, who was in charge of manufacturing the stacks of perforated papers.

7. Some people, not knowing the Bombe's Polish history, suggested that the name for the British Bombe came from the sound the machines made as they ticked their way through the possible rotor settings, like an old time-bomb ticking. However, Gordon Welchman, in his book The Hut SLY Story (McGraw-Hill, 1982, 77), says, "Our bombes [the British versions] were said to make a noise like a battery of knitting needles." U.S. Navy Wave Veronica Mackey Hulick, who operated the American crypt-analytic Bombes, agreed that "the noise from the Bombe was like thousands of clacking knitting needles." However, CDR McDonald, a Bombe watch officer, doesn't recall a clicking sound, but remembers it made a lot of loud noise.

8. Because there were several different models used throughout the war, the speed of the machine varied depending on the model. This speed (50.4 rpm) refers to the British 39-point machine. (Correspondence to the author from John Harper, Bombe Rebuild Project Manager, Bletchley Park Trust. 12 February 2000.)

9. Leo Rosen and William Friedman, "Cryptanalysis of German Army & German Air Force ENIGMA Traffic" SSA (report on) "E" Operations of the GCCS At Bletchley Park, 1945, 59. (NARA Record Group 457; File #3620.)

10. Memorandum from OP-20-G, "Brief Resume of Op-20-G and British Activities vis-a-vis German Machine Ciphers," July 15,1944, 1.

11. Anderson, Deborah, "Joseph Desch and Magic," Miami Valley History (1993), 11.