THE microscope is an invaluable agent in the detection of crime. Some years ago, it was discovered by the authorities of a railway in Germany that a barrel which, on being dispatched from a certain station, contained silver coin, had, during the journey to its destination, been emptied of its contents and filled with sand. For some time no clew to the perpetrator of the robbery could be discovered; but at length a learned professor having been consulted on the subject, called in the aid of the microscope. The professor went to work on the right track at once. He, knowing that, even though in the very minutest degree, there was a distinctive difference in the sand found near the various stations along the railway line, sent for samples of it from each of the places through which the train containing the silver coin had passed. With the microscope he then carefully examined each sample, compared it with the sand found in the barrel, and thus identified the station from which the latter had been procured. Having, in this ingenious manner, found out the station he wanted, little difficulty remained; for the railway servants employed at it, by one of whom the robbery had been committed, were so few in number that the culprit was readily detected. In this ingenious manner the thief was found out.