It is one of the too numerous class of cases, of which mere boys are the heroes, (if the term may thus be perverted,)--a class that is represented in this work, which would otherwise be incomplete, professing, as it does, to illustrate the various phases of post-office life, as respects persons of different ages and conditions. The present narration will show that our own times are not the only period fertile in juvenile rascality, but that the youth of thirty years ago were too frequently set upon evil. At the time when the incidents occurred which I am about to narrate, (viz. in the year 1826,) it was the usual practice in the New York office to make up the morning's mails on the preceding evening, and to place them upon tables before they were entered on the "transcripts," (sheets or books in which copies of the post-bills are made,) and enclosed in wrappers. At this time a boy twelve or thirteen years of age was employed as assistant to one of the letter carriers, and generally arrived at the office at an earlier hour in the morning than the regular clerks. The nature of his duties made him well acquainted with the different species of letters, so that he could determine without much difficulty, from its general appearance, whether a letter contained hidden treasures or not. So, by way of beguiling the time before the arrival of the clerks, or for the sake of a little improving practice, he one morning looked over the Eastern mail, which lay spread before him, and selected a letter addressed by the Cashier of the Farmers' and Mechanics' Bank of New York, to the Cashier of one of the banks in Boston, containing four thousand dollars in bank-notes of one thousand dollars each. On the discovery of this "pile," the boy lost no time in "removing the deposits" to his own pocket, substituting for the bank-notes four pieces of paper of an equal size, cut from wrappers lying on the floor. He then resealed the letter and replaced it. The letter was forwarded by due course of mail, and when it was received at the bank, the Cashier discovered to his dismay that the money by some jugglery had been converted into brown paper; and the evident marks of breaking open and resealing, indicated unequivocally that some human agency had been engaged in working the spell.