letter X, 8 of K, 16 of B, 13 of C, 80 of I, N, O, and S; 85 of A, 90

of T, and 120 of letter E.

The compounds most frequently met with are NG EE LL MM TT DD and NN.

The order of frequency in which the letters of the alphabet occur as initial letters in words is as follows:

S, C, P, A, D, I, F, B, L, T.

_Employment of Cipher Disk._

If messages are enciphered by a mere transposition of the letters of the alphabet, the cipher disk can be used to quickly decipher the message, as the following example will show: Assuming that F is used to represent A, G to represent B, H to represent C, I to represent D, J to represent E, etc., in regular sequence, and that the message to be enciphered is: "We are short of rifle ammunition; send 30,000 rounds at once."

This would be enciphered if divided into groups of four letters as follows:

jbfo bnyr omra oxub fuls xmxr snbs cmjb smhm yrln fsco rlsc nfmr sdb.

Place "a" of the upper cipher disk under B of the lower disk and notice whether the cipher letters jbfo--the first group--are intelligible. They give "sawn," continue this for "saw," the first three letters, may be the text word. Now the next group is B N Y R and these give A O D K. We know that A does not represent B because the first 8 cipher letters give the meaningless letters "sawnaodk." Turn "a" to C and we have for the first group T B X O, which is without meaning. Turning "a" to D we get U C Y P, a meaningless jumble. Turn "a" to E and we get V D Z Q, which is meaningless. Now turn "a" under F and we find that JBFO mean "Wear," which, so far at least, gives us a part of a word, or the word "We" and part of another word. We continue to the next group B N Y R, which gives us "esho." We now have these letters "Wearesho," which at a glance we read "We are sho;" continuing to the next group O M R A the cipher disk gives us "rtof," and we read "We are short of" and know we have found the key letter, and the information hidden in the cipher is ours. Continue deciphering with "a" under F until the end of the message. Sometimes the key letter is changed after two, three, or four letters.

It is a matter of minutes only to run through the alphabet and learn the meaning of a message so enciphered.