Respectfully returned to the commanding general, Department of the Columbia, approving the opinion of the commanding officer, Twenty-first Infantry, and of the judge advocate of the division, in respect to the duty of and method to be adopted by sentinels in preventing prisoners from escaping. * * * * * By command of Maj. Gen. Schofield: J. C. KELTON, _Assistant Adjutant General_. See also Circular No. 53, A. G. O., December 22, 1900. =306.= On approaching the post of the sentinel at the guardhouse, a sentinel of the prisoner guard or an overseer in charge of prisoners will halt them and call, "=No. 1, (so many) prisoners.=" He will not allow them to cross the post of the sentinel until so directed by the corporal of the guard. =307.= Members of the prisoner guard and overseers placed over prisoners for work will receive specific and explicit instructions covering the required work; they will be held strictly responsible that the prisoners under their charge properly and satisfactorily perform the designated work. =Section 17. Stable guards.= STABLE GUARDS. =308.= Under the head of stable guards will be included guards for cavalry stables, artillery stables and parks, mounted infantry stables, machine-gun organization stables and parks, and quartermaster stables and parks. Where the words "troop" and "cavalry" are used, they will be held to include all of these organizations. =309.= When troop stable guards are mounted they will guard the stables of the cavalry (see Par. 13). When no stable guards are mounted the stables will be guarded by sentinels posted from the main guard under the control of the officer of the day. The instructions given for troop stable guard will be observed as far as applicable by the noncommissioned officers and sentinels of the main guard when in charge of the stables. TROOP STABLE GUARDS. =310.= Troop stable guards will not be used except in the field, or when it is impracticable to guard the stables by sentinels from the main guard. =311.= Troop stable guards will be under the immediate control of their respective troop commanders; they will be posted in each cavalry stable or near the picket line, and will consist of not less than one noncommissioned officer and three privates. Stable guards are for the protection of the horses, stables, forage, equipments, and public property generally. They will, in addition, enforce the special regulations in regard to stables, horses, and parks. =312.= Sentinels of stable guards will be posted at the stables or at the picket lines when the horses are kept outside. The troop stable guard may be used as a herd guard during the day time or when grazing is practicable.