In the narrations of mail robberies which we have thus far given, their perpetrators, though bold and unscrupulous, have not often plotted the destruction of human life in order to further their projects. But in the case we are about briefly to relate, murder on a large scale was coolly contemplated for the sake of the facilities which would be afforded to the plunderers of the mail, by the confusion, distress, and preoccupation which necessarily follow the throwing of cars from a railroad track. The certain destruction of property and the probable loss of life which would be caused by the successful execution of their plans, were nothing to these atrocious scoundrels, as long as by these means plunder might be brought within their grasp. Rather more than a year ago, on a certain day in March, the locomotive of a mail train upon one of the Western railroads was thrown from the track by a "T" rail, which was placed with one end against a tie, so that the other, projecting somewhat upward, was struck by the engine. This occurred near a city in one of the Western States. No one on the train was injured, and whoever placed the obstruction failed in accomplishing his purpose, if that was to rob the mail. No person was particularly suspected of the deed, but tracks made by a boot of peculiar shape, with rows of large nails around the soles and heels, were found in the soft clay in the neighborhood of the spot, and an impression of them was taken for future reference. On the same day the Superintendent of the road received a letter, of which the following is a copy. Adrian, March 7, 1854. Sir: I have for the last few days written five or six notes to send you, but as often I have changed my mind and concluded to let the information that I wish to convey you, lie buried in obscurity. But the late act of villany that was committed I may say within sight of our city, forces me to disclose to you information that I received a few days ago of the formation of a gang of rascals who have combined together to commit, I may say, wholesale murder, and other criminal acts, by obstructing the passage of trains and endangering the same on the M. S. & N. R. R. This gang of villains is under the management of two men that are now known to me. The subject came to my knowledge by an offer from them of a large sum of money if I would take part with them in their intended villany.