To this bureau was gathered all the information of the signal corps and of the hundreds of scouts and spies who traversed the rebel army and country. Trusty and intelligent men were picked from the rank and file of the army and placed under command of General Sharpe. The first piece of work undertaken by the general was to obtain a full roster of Lee's army as it lay on the Rappahannock, the numbers and titles of regiments and the names of the corps, division, brigade, regimental and company commanders. He picked out General Heath's brigade of A. P. Hill's corps as the first one to operate on, and by daringly scouting in person through the lines of that brigade, conversing with its pickets, and mingling with its men, he succeeded in obtaining not only a full list of its officers, and an accurate detail of its strength, but a correct description of the personal appearance and habits of these officers. After mastering Heath's division he picked out an intelligent soldier whom he crammed with all he knew himself about the division, dressed him up in a rebel uniform, and sent him into another division of Hill's corps. Of course the man was at once apprehended and taken before a provost marshal, but made such a plain statement, giving the names of the officers of the regiments in Heath's division, to which he claimed to belong, and describing their personal appearance and habits with more accuracy than reverence, that he was dismissed, with a reprimand for his want of respect for his superior officers, and ordered to report back at once to his regiment. After looking around him and ascertaining everything worth noting with regard to the command, he returned to General Sharpe; and thus the particulars, as ascertained by every new scout, facilitated the means of getting more. At length Sharpe had a roster of the whole of Lee's army, and could tell its strength at any time within a thousand or so, that thousand being the changing mass of stragglers, furloughed, and sick, to whom no special location could be assigned. He could also tell the name of every officer in that army, and rebel generals of divisions might have gone to him for information concerning their own subordinates. The great usefulness of thus possessing the precise knowledge of the strength and formation of the enemy's forces was particularly illustrated at Gettysburg, where the anxious spirits of the Union commanders were relieved by ascertaining from General Sharpe that every brigade but one of Lee's army had been engaged in the fight, and that that general had no reserve with which to follow success or break defeat. Not least among the resources from which valuable information was obtained were the contrabands, whose fidelity and truthfulness were remarkable, considering their want of education,