The ‘"Union"’ gun overboard.
--A monster gun called the ‘"Union,"’ cast at Pittsburg, and weighing upwards of fifty thousand pounds, fell overboard whilst being shipped at Baltimore for Fortress Monroe last Friday. The water where the gun fell in was about six feet deep, but there was under it a soft mud, which was sounded to the depth of six feet more; and the gun that evening was about twelve feet below the surface of the water.