Arrest of a head Detections.
--During the passage of the flag-of-truce boat which left this city for City Point on Monday last Capt, Philip Cashmere, a detective, was noticed as being particularly desirous of mingling among the prisoners, and just before reaching the point , he was observed to pass into the hands of one of them a large package, which fact was immediately communicated to Capt. Hatch, the officer in command of the Yankee prisoners to be sent North.--In a short while after, while the prisoners were being transferred to the Federal steamer which had been sent to take them to Fortress Monroe, the one who was seen to receive the package was made to stand aside, and informed that unless he handed over the bundic which had been given him by Cashmere the whole of them would be taken back to Richmond. The document was readily given up, and then they were permitted to leave our boats.The perused of the paper which were enclosed in the envelope that Cashmere handed to the Yankee prisoner led to his immediate arrest, and as soon as the boat arrived at Rocketts yesterday afternoon he was taken to Castle Thunder and committed till such time as a hearing of his case can be had. The papers are reported to contain important orders which have emanated from Gen Winder's department and other matters of an alleged treasonable character.
We learn that Cachmeyer states that the documents in question were not intended to be communicated to the enemy for the injury of the South, but that they were only to be sent to some of his friends in Baltimore, as an explanation of certain acts which he had committed here.
Cashmeyer has been looked upon by Gen. Winder as one of his most reliable detectives, and be has heretofore been entrusted with the most important missions.
