Range-finder. An instrument for determining ranges. There are several different principles which may be used. The distance may be measured, 1st, by the visual angle subtended by objects of known height; 2d, by the velocity of sound; 3d, the instrument may furnish a base-line in itself and solve a triangle in which the base and two adjacent angles are given. The term is also applied to instruments used to solve a triangle, the base of which is obtained by outside means. Range-finders constructed on the visual angle principle have been known for many years. Boulanger’s instrument uses the 2d principle. It consists of a glass tube closed at both ends filled with a liquid in which a small umbrella-shaped piece of metal is submerged. The tube is held vertically in the hand, the metal slowly sinks to the bottom. When the flash of the enemy’s gun is seen, the tube is inverted and the metal moves towards the other end. When the sound is heard, the tube is brought to the horizontal. The distance through which the piece of metal has moved gives the range by means of a scale on the side of the tube. Berdan’s range-finder is an expensive instrument using the 3d principle. It is mounted on a wagon, and intended to accompany either foot-troops or artillery. It has found great favor in Germany. Nolan’s range-finder consists of an instrument for automatically solving triangles. A similar thing was devised about 1870 by two American officers, Maj. Morgan of the 4th Artillery, and Capt. Lorain of the 3d Artillery. The most ingenious, complete range-finder has been proposed by Lieut. Gordon of the 4th Artillery. He uses two fixed angles and a variable base-line supplied by the instrument itself. The principal parts of Nolan’s range-finder are: Two instruments for measuring angles, one tape-line, and one reckoning cylinder. Each of the two instruments consist of two telescopes, which lie crosswise one above the other under an angle of about 90°; the smaller of the two has a long arm, with a vernier at one end; to the other a sector is fastened, which is divided up into degrees. By means of a screw, an angle of about 20° can be described by the upper or smaller telescope. The reckoning cylinder consists of a solid body and two rotating rings. The lower ring and the lower edge of the body are divided into 100 equal parts. On the upper ring are the logarithms of the figures, and on the upper edge of the body are the logarithms of the signs, from 6″ up to 2° 15′.
To find the range, the instruments on their tripods are arranged at the end of the assumed base-line, which is perpendicular to the range; or the instruments may be attached to the right and left guns of a battery. The long telescopes are turned toward the object whose distance is to be found; the smaller ones upon each other, and the cross-threads of each made to cover the cross-lines on the leather disk through which each small telescope points. The coincidence obtained by directing the longer telescope on the object, the two angles at the base are determined; the base-line being measured, one side and two angles of the triangle are obtained. With this data recourse is then had to the reckoning cylinder. The arrow marked “band” is set on the figure that corresponds with the distance between the instruments or base-line,—say 34 yards; then set the arrow on the lower ring on the figure corresponding with the angle found through the instrument,—say 18°; then find the figure for the number of degrees of the other angle,—say 42° on the lower ring. Just above that is the figure 60 on the other division of the lower ring; coinciding with this on the lower edge of the upper ring is the distance, 1320 yards. The bases used are from 30 to 40 yards for a range of 2000 yards and over.
Watkins’s range-finder and Gautier’s telemeter are instruments which require a measured base-line. See [Telemeter].
Ranger. One of a body of mounted troops, who were formerly armed with short muskets, and who ranged over the country around, and often fought on foot.
Ranging. The disposal of troops in proper order for an engagement, manœuvres, or march, etc.
Rank. Range of subordination, degree of authority. The relative situations which officers hold with respect to each other, or to military things in general. Questions as to the positive or relative rank of officers may often be of the greatest importance at law, in consequence of the rule, that every person who justifies his own acts on the ground of obedience to superior authority must establish, by clear evidence, the sufficiency of the authority on which he so relies. There may also be many occasions on which the propriety of an officer’s assumption of command, or his exercise of particular functions, or his right to share with a particular class of officers in prize-money, bounties, grants, and other allowances, may depend on the correctness of the view taken by himself or others of his rights to a specific rank or command; and an error in this respect may expose him to personal loss and damage in suits before the civil tribunals. The regulation of military rank is vested absolutely in Congress, which confers or varies it at pleasure. The will of Congress in this respect is signified by the creation of different grades of rank; by making rules of appointment and promotion; by other rules of government and regulation; or is by fair deduction to be inferred from the nature of the functions assigned to each officer; for every man who is intrusted with an employment is presumed to be invested with all the powers necessary for the effective discharge of the duties annexed to his office. Rank and grade are synonymous, and in their military acceptation indicate rights, powers, and duties, determined by laws, creating the different degrees of rank, and specifying fixed forms for passing from grade to grade and when rank in one body shall give command in another body; and also when rank in the army at large shall not be exercised. Rank is a right of which an officer cannot be deprived, except through forms prescribed by law. When an officer is on duty, the rank itself indicates his relative position to other officers of the body in which it is created. It is not, however, a perpetual right to exercise command, because the President may, under the 62d article of war, at any time relieve an officer from duty; or an officer may be so relieved by arrest duly made according to law; or by inability to perform duty from sickness, or by being placed by competent authority on some other duty. But whenever an officer is on duty his rank indicates his command.
Rank. A line of soldiers; a row of troops reckoned from side to side, or in breadth;—opposed to file. The ranks, the order of common soldiers; as, to reduce a non-commissioned officer to the ranks. To fill the ranks, to supply the whole number, or a competent number. To take rank of, to enjoy precedence over, or to have the right of taking a higher place than.
Rank and File. The body of soldiers constituting the mass of the army, and including corporals and privates. In a more extended sense, it includes sergeants also, excepting the non-commissioned staff.
Rank, Brevet. See [Brevet].
Rank, Double. A rank composed of front and rear files.