know, is used by both the Navy and the Army. The device itself merely depends on the use of two disks, on the same center. There's a series of numbers on one; on the other an arrangement of letters and certain codified service-words. Now, once a key-relation is determined on, the sender picks out his message, and the receiver, placing his disks according to the predetermined key-relation, reads this otherwise undecipherable message without any great trouble. What made the loss of this code of ours especially costly, however, was that the 'filler' or 'blind' words incorporated in the cipher—very much after the fashion of the duck that barked like a dog, in the old conundrum—took months and months of hard work for the two Departments to work out."
"But what was the use of these blind words, as you call them, in a code like that?" asked Wilsnach.
"Merely to insure secrecy! These fillers are put in as a stumbling-block, for the code-expert of the enemy to bark his shins on. For, once your enemy has messages enough to work with, he can eventually decipher any code ever devised by human intelligence."
"Now we do seem to be getting down to hard-pan," Kestner suddenly exclaimed. "You say this
