(b) If no means are at hand to correctly measure the angle of site of a distant point, the quadrants may be adjusted by using two guns as follows: Unlimber two guns at about the same level, first seeing that the sights are in adjustment (par. 75). Lay both guns upon some distant point by means of the panoramic sight set at 0 range. Now set both quadrants for the same angle of site (roughly estimated A. S. of the distant point) and center the bubbles of the range level by turning the handwheel of the range disks. By means of the quadrant wrench, adjust the range disk of one of the quadrants to agree with the other. Whatever error exists will now be the same in each quadrant. Now move one of the guns about 100 yards away and turn the muzzles toward each other. With the sights set at 0 range, lay the panoramic sights upon each other and measure the angle of site of each gun. Half the difference of the two readings will be the slope of the line of sight between the two guns. On the level scale of the quadrant which read the greater angle of site, set off 300 plus the half-difference, on the other quadrant set off 300 minus the half-difference. Now center the bubble of the range level by turning the handwheel of the range disk. By using the quadrant wrench, adjust the range disk until it reads 0 range. Having thus adjusted two guns, the others may be adjusted by the first means described. OBSERVING INSTRUMENTS. B. C. Telescope, M. 1915. =The B. C. Telescope, M. 1915=, is a binocular observing instrument of the scissors type. The two tubes of the telescope may be clamped either in a vertical or a horizontal position. In the former position the objectives are 12 inches above the eyes of the observer, and in the latter position they are 24 inches apart and at the same height as the eyes of the observer. In both cases they permit the observer to take advantage of some shield or other cover and still obtain a full view of the sector of observation. The tubes may be adjusted for the observer’s interpupillary distance in either the vertical or the horizontal position. The eyepieces may be adjusted to the eyes of the observer by screwing in or out. [Illustration: _BATTERY COMMANDER’S TELESCOPE MODEL OF 1915._ _36-22-31_ ] =The principal parts of the telescope are=:—Leveling mechanism, azimuth mechanism, elevating mechanism, angle of site mechanism, the telescopes and the tripod. A carrying case is provided separately for the instrument and for the tripod. In garrison a storage case is also provided. _The leveling mechanism_ consists of a ball and socket joint operated by the vertical spindle clamping screw.