BETWEEN THE SCENES.Progress of the story through the Post. I. Extract from the Advertising Columns of “The Times.” “AN UNKNOWN FRIEND is requested to mention (by advertisement) an address at which a letter can reach him. The receipt of the information which he offers will be acknowledged by a reward of Five Pounds.” II. From Captain Wragge to Magdalen. “Birmingham, July 2d, 1847. “MY DEAR GIRL—The box containing the articles of costumes which you took away by mistake has come safely to hand. Consider it under my special protection until I hear from you again. “I embrace this opportunity to assure you once more of my unalterable fidelity to your interests. Without attempting to intrude myself into your confidence, may I inquire whether Mr. Noel Vanstone has consented to do you j