These officials were ordered to visit Colonel Ingraham's office and examine the little evidence on hand. They and their tried officers formed a junction on Sunday afternoon with the large detective force of Provost-Marshal Major O'Bierne. The latter commands the District of Columbia civil and military police. He is a New-Yorker and has been shot through the body in the field. The detective force of Young and Murray consisted of Officers Radford, Kelso, Elder, and Hoey, of New-York; Deputy-Marshal Newcome, formerly of THE WORLD'S city staff; Officers Joseph Pierson and West, of Baltimore. Major O'Bierne's immediate aids were Detectives John Lee, Lloyd, Gavigan, Coddingham, and Williams. A detachment of the Philadelphia detective police, force--Officers Taggert, George Smith, and Carlin, reporting to Colonel Baker--went in the direction of the North Pole; everybody is on the _que vive_ for them. To the provost-marshal of Baltimore, MacPhail, who knew the tone and bearing of the country throughout, was joined the zealous co-operation of Officer Lloyd, of Major O'Bierne's staff, who had a personal feeling against the secessionists of lower Maryland; they had once driven him away for his loyalty, and had reserved their hospitality for assassins. Lieutenant Commander Gushing, I am informed, also rendered important services to the government in connection with the police operations. Volunteer detectives, such as Ex-Marshal Lewis and Angelis, were plentiful; it is probable that in the pitch of the excitement five hundred detective officers were in and around Washington city. At the same time the secret police of Richmond abandoned their ordinary business, and devoted themselves solely to this overshadowing offense. No citizen, in these terrible days, knows what eyes were upon him as he talked and walked, nor how his stature and guise were keenly scanned by folks who passed him absent-faced, yet with his mental portrait carefully turned over, the while some invisible hand clutched a revolver, and held a life or death challenge upon his lips. The military forces were commanded by Colonel Welles, of the Twenty sixth Michigan regiment, whose activity and zeal were amply sustained by Colonel Clendenning, of the Eighth Illinois cavalry, probably the finest body of horse in the service. The first party to take the South Maryland road was dispatched by Major O'Bierne, and commanded by Lieutenant Lovett, of the Veteran Reserves. It consisted of twenty-five cavalry men, with detectives Cottingham, Lloyd, and Gavigan; these latter, with the lieutenant, kept well in advance. They made inquiries of a soothing and cautious character, but saw nothing suspicious until they arrived at Piscataway, where an unknown man, some distance ahead, observed them, and took to the woods. This was on Sunday night, forty hours after the murder.