292. There are no more important duties, which an officer may be called upon to perform, than those of collecting and arranging the information upon which either the general, or daily operations of a campaign must be based.  For the proper performance of the former, acquirements of a very high order, in the departments of geography and statistics, are indispensable requisites; to which must be added a minute acquaintance with topography, and a good coup d'eoil militaire for that of the latter.
293. However detailed and perfect may be a map, it can never convey all the information that will enable   an officer to plan, even an ordinary march, with safety; still less, operations that necessarily depend, for their success, upon a far greater number of contingencies.  To supply these deficiencies of maps, an examination of the ground must be made by the eye; and verbal information be gained, on all the points connected with the operation over this ground.  This examination and collection of facts is termed a Reconnaissance.
294.   From the services demanded of a reconnoitring officer, it is, in. the first place, evident, that he should possess acquirements of no ordinary character; but in addition to these he should be gifted by nature with certain traits, without which his acquisitions would be of little account, in the discharge of the responsible duty in question.
295.  With clear and specific information before him, one-half of a general's difficulties, in planning his measures, are dissipated.  In a letter from General Washington to Major Tallmadge, now to be seen framed in the office of the Commissary-General of New York, he remarks, in relation to reports made to him, on a certain occasion: "But these things, not being delivered with certainty, rather perplex than form the judgment." It is in truth this feeling of certainty that constitutes all the difference; having it, the general makes his dispositions with confidence; without it, he acts hesitatingly; and thus communicates to others that want of confidence felt in his own mind.
296.  An officer then, selected for the duty in question, should be known to be cool-headed and truthful; one who sees things as they are, and tells clearly and precisely what he has seen.   In making his report, whether verbally or in writing, the officer should study conciseness and precision of language.  He must carefully separate what he knows, from his own observation, from that which he has learned from others; and add all the circumstances of place, and time, with accuracy.
297. Duties of Reconnoitring Officer.  The first thing to be done by an officer, selected for a reconnaissance, is to ascertain precisely the duty required of him; and what further should be done in case of certain contingencies that may, from the nature of the duty, be naturally looked for.  In the performance of the duty assigned him, and in making his report, the officer should keep always in mina the specific character of his mission, as his guide in both points.
298. As the need of a reconnaissance supposes a deficiency in information upon the features of the country, the officer, detailed to make one, should provide himself with maps, a good telescope, such simple aids for judging of distances, and ascertaining the relative distance of objects, as he can himself readily make; writing materials; one or more good guides; and gain all the knowledge he can, upon his mission.
299. The talent of judging of distances, and of the connection between the various features of a country within the field of vision, is partly a natural and partly an acquired one.  Some individuals can never be brought to have any confidence in their own judgment on these points; others have a natural aptitude for them, which requires but little practice for their perfect development.  The powers of the eye vary so greatly among civilized persons, that no general rules can be laid down, as a guide for the matter in question.  Among uncivilized hordes, used to a roaming life, there are found standards which are well understood by all, - the Arab, for instance, calling that distance a mile, at which a man is no longer distinguishable from a woman growing out of their habits.
300.  The first thing then to be done by an officer, in acquiring the coup d'oeul militaire, is to learn, both from books and on the field, what space is taken up by a battalion and its intervals, by a squadron, and by a battery when in order of battle; how much when in column of march; and the average time required for certain movements, under given circumstances of the ground.  This acquirement he may make by adopting some standard of his own; his ordinary pace, and that of a horse, serving for computing time and distance   reciprocally.  The next step is to acquire the habit of estimating, by the appearance of these different objects, from various points of view, how far off they are.  This must be done practically.  A very simple aid to it is the following; - Upon the stem of a lead-pencil, cut square, and held out at a uniform arm's length from the eye, and by means of a thread attached to it and fastened to the top button-hole, let the officer mark off, on one of the edges, the length seen on it by holding the pencil upright between the eye, and a man placed successively at different distances from it, as 100, 150 - 1000 yards.  This will give one rough standard fir practice.  Another may be made by first ascertaining the average height of certain cultivated trees, as the apple, &c. 

301. For getting relative positions, a contrivance for measuring angles roughly must be used. This is done by first folding a leaf of paper across, and then doubling it along the folded edge, as if to divide it into four equal parts.  The angle between the edge of the first fold and that of the second will be a tolerably accurate right angle.  Now by cutting off carefully along the fold, one of the pieces, we obtain a quadrant or 900; then folding this at the angle, so that the two edges will exactly coincide, we get the half of a quadrant or 450; and so on, by successive bisections, we can mark off smaller angles.  Then making a pen or pencil-mark along each of the folds, and numbering the angles successively from 0 to 900, we have a rough protractor, that can be used both for measuring angles and setting them off on a sketch.  To measure vertical angles, a thread with a light plummet, must be attached to the angular point.  If the object is above the horizon of the eye, we hold the protractor with the angular point from the eye, so that the plumb-line will fall along the face of the paper just touching if; then directing the top edge of the protractor on the object, so that it is just seen by the eye sighting along the edge, and the angle formed between the plumb-line and the other edge, will be the same as the angle between the line of sight and the horizon of the eye,
If the object is below the horizon of the eye, the angular point is placed towards the eye; the same series of operations will give the angle below the eye's horizon.
302. Guides.  Trustworthy guides are invaluable, but most rare, in an enemy's country.  The best, from the information they acquire by their habits of life, are to be found among those classes whose avocations keep them much abroad, going from place to place within a certain sphere constantly; such as common carriers, hunters, smugglers, &c.  Among the first thing to be attended to by an officer, in taking post at any point, is to find out persons of this class, and to ascertain their whereabouts when wanted.  Kind treatment, douceurs, and promises, should not be spared, to enlist either their good will or their interests; and, if policy requires it, they may openly be treated with apparent harshness, to screen them from odium among their neighbors
303. If none of this class can be found, then resort must be had to a higher; local authorities being in preference selected, and if necessary forced to act.  Here very careful treatment is requisite; when the necessity of the case is admitted by them, much may be gleaned by kindness, courtesy, and a certain deference, from such persons, that cannot be looked for from their inferiors.
304. Before starting on his mission, the officer should question his guide thoroughly; and if he has several, question each apart; like precautions should be taken with respect to other inhabitants.  Care must be had to find out the usual beats of one taken as a guide, so as not to take him out of his own neighborhood.  In all cases, the guide must be well watched, however trustworthy he may seem.  If unwilling, or sulky, he must, if needs be, be tied, and attached to a strong man, with a rope round his middle; being first strictly searched for any cutting instrument about him.
305.  Should there be but one guide, he must necessarily be placed with the most advanced portion of the detachment accompanying the officer.  If there are several, one must be there also; the one apparently the most intelligent with the officer, who should ply him with questions; and the others in the rear strictly guarded.
306. It may be well to remark, that guides are useful even in a country of easy communications; as, incase of a rencontre, they may point out bye-ways convenient for retreat, if necessary.
307. Reconnaissance.  To designate all the objects to be embraced in a reconnaissance, would lead farther than the limits of this little work will allow; some general heads, which will serve as guides in all cases, will therefore be alone noticed.
308. A general view of the ground to be examined must first be taken in, so as to obtain some notion of the forms of the parts, their connection, and relations to each other, before going into a detailed examination.  To one possessed of some topographical knowledge, this study of what is before him will not demand much time.  A level country, for example, he knows is usually well cultivated, and therefore has plenty of hedges, ditches, &c., which lend themselves well to affairs of light troops, - may be not a little inconvenient to maneuvres of artillery; - and frequently bring up cavalry very unexpectedly in full career.  In a mountainous one, dangerous passes, narrow roads, torrents with rough beds, ugly sudden turns, &c., will necessarily be met with.  Each and all of these demand a particular examination, and in his report their advantages and disadvantages should be clearly pointed out by the officer.
309. If the reconnaissance is for an onward movement; the distances from halt to halt, as well as all others, should be estimated in hours of march; the nature of the roads, and the obstacles along them be carefully detailed; the means that may be gathered along the line to facilitate the movement, as vehicles, men and materials for removing obstacles, &c.  The points where crossroads are found, must be specified; the direction of these roads; their uses, &c.
310. All local objects along the line. as villages, farm-houses, &c., should be carefully designated, both as to their position on the line, or on either side of it; and also as to their form, and color, &c., as "square white house on the right;" "round gray stone tower on hill to left."
311. The names of localities, in the way in which the inhabitants pronounce them, should be carefully written, and called over several times, so as to be sure to get them as nearly as practicable right in sound; then the names, as written by an intelligent inhabitant, should be added.
312. All halting points must be well looked to their military capabilities, in case of attack; as well as their resources for accommodating the troops, be thoroughly gone into.
If the halt is to take position for some time, to await or watch the enemy, then more care must be taken, the whole site be well studied as to its fulfill in the proposed end; the points of support on the flanks be designated, as well as others in front and rear, that may require to be occupied; the suitable localities to be chosen for parks, hospital, &c. ; the communications to be opened or repaired, pointed out; and all the facilities either for an advance or a retrograde movement, be laid down.
313. Armed Reconnaissance. Reconnaissances, made in the neighborhood of an enemy, require to be done under the protection of a proper detachment; the strength and composition of which will depend on the object to be attained.
314. If the object be to gain secretly a knowledge of the enemy's whereabout and strength, then a detachment of light cavalry, conducted by a trusty guide, through circuitous bye-ways, and in with celerity, but with proper precautions against falling into an ambush, or having its retreat cut off, is usually resorted to.  The details for this will be found udder the head Patrols.
315. When an enemy's position is to be reconnoitred, with a view to force him to show his hand, by causing him to call out all his troops; then a large detachment of all arms, adequate to the task of pressing the enemy vigorously, and also of withdrawing with safety when pressed in turn, must be thrown forward
316. Under the shelter of either of these forces, the officer, charged with the reconnaissance, takes the best moment, and best point of view, for carefully ascertaining the dispositions made by the enemy.  A good time will be at early dawn, when troops, in most services are all made to stand to their arms.  The points which the officer must exhibit most attention in finding out, are those occupied by the batteries, and all those in any way intrenched.
317. Patrols.  Patrols are of two classes, from the different objects had in view.  The first are those made with a view of insuring greater security from the enemy's attempts to pass, or force the line of out-posts, and may therefore be termed defensive patrols.  They consist usually of three or four men, who go the rounds, along the chain of sentinels and between the posts; seldom venturing farther than a few hundred paces beyond the sentinel's chain; the object being to search points which might present a cover to the enemy's scouts, and to keep the sentinels on the alert.
318. The second class are those made exterior to the line of out-posts, with a view of gaining intelligence of the enemy's whereabouts; and may therefore be termed offensive patrols.   They are composed of larger bodies of men then the first class, the number being proportioned both to the distance to be gone over, and the extent of front to be examined.  In a position, presenting but few cross-roads, and sparsely settled, a patrol of ten or twenty horsemen, may be found ample, to search, with all desirable thoroughness, from twenty to forty miles in advance of the position, along the principal avenues to it; whereas, with a more extended front, presenting many lateral avenues, double this number might be required for the same duty.  From the information obtained, through the ordinary channels of maps, and by questioning the inhabitants at hand, the commanding officer can usually settle, with sufficient accuracy, the strength of a patrol
319.  From the duties to be performed by patrols, cavalry are usually employed alone; in cases of very broken country infantry may be necessary but they should always be accompanied by some horse, if for no other purpose than to transmit Intelligence promptly to the rear.
320. The main duties of a patrol are to find the enemy if in the neighborhood; gain a good idea of his position and strength; to make out his movements, and to bring in an accurate account of his distance from the out-posts of their own force; and the character of the ground between the position occupied by the respective forces.
321. From the nature of these duties, it is evident that both officers and men, for a patrol, should be selected with especial reference to their activity, intelligence, and the aptitude they may possess, from previous habits of life, for a service requiring a union of courage, prudence, and discriminating observation - usually to be met with only in individuals who have been thrown very much upon their own resources.  When the character of the country admits of it, the employment of such individuals, singly, or in very small bodies, as scouts, is one of the most available means of gaining intelligence of an enemy, without betraying the secret of our own whereabout.
322.   Duties of Officer in command of a Patrol.  In conducting a patrol, the commanding-officer should provide himself with a good map, telescope, and guides; and gain all the information he can before starting, by questioning persons in the neighborhood.  Nothing should escape his eye along his line of search; and he should particularly note points which might be favorable to his defence, if driven back by enemy; or by which his retreat might be endangered.
323.  The order of march of the patrol will be regulated by the circumstances of its strength, kind of troops employed, the character of the country passed over, the hour of the day, and the particular object in view.  The intelligence and judgment of the officer in command will have sufficient exercise on these points; as he will be continually called upon to vary his dispositions.  The general and obvious rule-of keeping a look-out on all sides, will prompt the general disposition of an advanced-guard, rear-guard, and flankers, according to the circumstances of the case, however small his command.  The sole object being to carry back intelligence of the enemy, no precautions should be omitted to cover and secure his line of march, without making however, too great a subdivision of his force.
324. Too much circumspection cannot be shown in approaching points favorable to ambuscades; as woods, ravines, defiles, enclosures, farm-houses, villages, &c.  The main-body should always be halted, in a good position beyond musket-shot, or where cover can be obtained, whilst a few men proceed cautiously forward, following at some distance in the rear of, but never losing sight of each other, to examine the suspected spot.  If the officer deem it necessary, at any point, to detach from his command smaller patrols, to examine points at some distance on his flanks, he should halt the rest, at the point where they separate, until the detachments come in and report; or, if he decides to move forward, he should leave three or four men at the spot, to convey intelligence promptly to the rear, if anything is discovered, as well as to himself.
325. It may frequently be found that some eminence on the flanks may present a good view of the surrounding country, in which case, if it be decided to use it, two or three men ought to be detached for the purpose, with orders to keep in sight of each other, but far enough apart to guard against a surprise of the whole.
326.  When the officer finds himself in the presence of the enemy, he should halt his command at a convenient spot, where they will be screened from the enemy's view; and, having made his dispositions against a surprise, he will proceed with a few picked men to the most favorable point from which he can obtain a good look-out, to reconnoitre the position occupied, and the other points of interest.  If he deem it advisable to keep his position, or change it for some other point more favorable, he will first transmit a report to the rear of what he has observed.
327. When the patrol moves by night, the ordinary precautions must be redoubled.  Signals must be agreed upon to avoid danger, should any of the party become separated from the main body.  Careful attention must be given to everything passing around; as the barking of dogs, noises, fires, &c.  On approaching any inhabited spot, the command should be brought to a halt, whilst a few picked men move noiselessly forward, and if practicable, by stealing up to the windows, learn the character the inmates.
328.  It cannot be too strongly impressed upon the mind of the officer in command of a patrol, that be must be all ears and eyes; that he will be called upon in turn, to exercise great boldness, caution, presence of mind and good judgment, in accomplishing a mission where the enemy must be seen but not encountered; and such roads and halting points be selected, both in moving forward and returning, as shall be most favorable to his movements, and least liable to expose him to a surprise, or a disadvantageous collision with the enemy.