The post-office people are, if not omniscient, at least very obliging. I have found a letter directed to "Carrolton, in America," and the letter had been forwarded to, and bore the post-mark of every Carrolton in the United States before it was sent here. The work of the ladies falls under two heads: "Common" and "Special." We will get the best idea of what "Common" means, in contradistinction to "Special," by watching Miss A, on "Common" work this morning. Taking one of the bundles of letters from the basket, she opens it and takes up the top letter; spreading it on the desk, she finds the envelope inside; it is directed to "William Smith, Philadelphia, Penn.," and the words "uncalled for," stamped on the envelope, show why it was sent here. Now, the signature is to be looked for: it is here--"John Jones;" next, where was it dated?--"Somerville, Ohio;" but does the post-mark on the envelope correspond with that? Yes, it is post-marked from where it was dated; so, "John Jones" will receive his letter back again: his friend, "W. Smith," may have left Philadelphia, or may have died. "John Jones'" letter is returned to him in a coarse, brown "P. O. D." envelope, stamped with the letter A in one corner, and he pays three cents for the privilege of knowing that his friend "Smith" never received his letter. The next is a delicate pink affair, dated, "White Rose Bower"--signed, "Ella;" "only this, and nothing more;" so the letter is hopelessly dead, and thrown into the paper-basket at Miss A's side. The epistle following this is signed, "Henry Foster," and could be returned if it had not been dated at "White Hall" and post-marked "Harrisburg." On looking over the Post-office Directory, we may or may not find a White Hall in Pennsylvania, but there is nothing in the letter to show whether "Henry Foster's" home is in Harrisburg or White Hall; consequently, that letter is dead, too. Here is one, signed plainly and legibly, but the writer has omitted to date it from any particular place. From the tone of the letter, it is plainly to be seen that he lives where the letter was mailed--but where was it mailed? The post-mark on the envelope is so indistinct that any lady not employed in the Dead Letter Office would throw it aside as "unreadable;" but ladies here learn to decipher what to ordinary mortals would be hieroglyphic, or simply a blank. After consulting the pages of the Post-office Directory beside her, Miss A passes the envelope to Miss B. "Can you suggest any post-office in Indiana beginning with M, ending with L, with about four letters between?" Miss B scrutinizes the envelope closely. "The post-mark is not from Ind. (Indiana), it is from Ioa" (Iowa), is her decision. Misses C, D, and E, at work in the same room, differ in opinion, and at last Miss A steps across the hall to the room of the lady superintendent, where a "blue-book" is kept, and, with the assistance of this lady and the book,