“If the reader will look at an apparent flourish under the words, ‘My dear Father,’ as if underscored, he will observe three little dashes like this, - - - and a little further on a careless looking scratch of the pen, resembling . - -. This forms the key to the simple cipher, and the same characters are indifferently scattered about the sheet so as to attract only the eye of an operator. The three little dashes represent the Morse character for the figure five - - - (5), while the other signal, a dot and two dashes, is a W, which, when placed alone, is always understood to stand for word. Now the operator will be sure to see that 5, W, while the chances are that no one else but an operator would. The young friend to whom I had addressed this I knew would understand, from the tone of the letter, that it was a blind, and he would search for a different interpretation, and would soon discover the 5, W, which he would see referred to the fifth word. If the reader will read only every fifth word of this letter he will have the true meaning.

“Translation. — Been all through Southern Army, again obliged to delay here account sickness Impossible Confederate advance are exhausted half army absent sick balance are demoralized look under front portion Blank’s house situated on hill road Manasses to Washington black roll of papers official proofs wish Friend Covode secure them officers are there night students Georgetown signal South from the dormitory will be home soon as can.”

From Kerbey’s 1889 memoir The Boy Spy: A Substantially True Record of Secret Service During the War of the Rebellion.