23,751. Dreyer, J. T. Oct. 25. Sights.-Relates to sights provided with means for compensating for changes in muzzle velocity and errors of the day, and consists mainly in so graduating the range scale that the distances between adjacent graduations are inversely proportional at each particular range to the change in range due to a definite change in muzzle velocity. The invention also comprises (1) the provision of independentlyadjustable scales whereby the corrections relating to changes in muzzle velocity (including speed of ship along the line of fire), and errors of the day (including speed of target along the line of fire) may be applied directly to the sighting apparatus, and (2) the provision of two cam devices, one of which operates to apply the muzzle velocity corrections, and both of which operate to apply the corrections for errors of the day. The invention is shown in Figs. 1 and 5 as applied to naval gun-sights. The sight is mounted on a bar A pivoted at a to the sight bracket A<2>, and may be elevated by turning a handwheel c<5> actuating, through a shaft c<3> and worm gearing c<2>, a shaft c carrying a cam C engaging a roller a<1> on the sight bar A. The shaft c carries the range dial A<3>, which cooperates with a reader d<x> carried by a radial arm D fast with a sleeve d co-axial with the shaft c. The reader d<x> is carried on the third of three contiguous scales d<1x>, d<2x>, d<3x>, upon which may be set cumulatively the corrections relating to muzzle velocity, such as those for temperature of magazine, wear of gun, and speed of ship along the line of fire. The setting of the reader d<x> is thus the algebraic sum of these separate corrections. The sleeve d is also connected by a link d' to a shaft d' carried by the bracket A<2> and having fast with it an arm d<6> carrying a roller pressed by a spring device e<x> against a cam a<2> depending from the sight bar A. The shaft d<5> carries three scales e<1>, e<2>, e<3> upon which may be set cumulatively the corrections for errors of the day, such as those for pressure and temperature of the air, speed of target along the line of fire, and change in the configuration of the head of the projectile. The effect of these settings is that the point of connexion between the link d' and shaft d<5> is shifted from a position of coincidence with the axis of the shaft d<5> by an amount which represents the algebraic sum of the separate corrections. The arm D will consequently be angularly displaced by a corresponding amount which, owing to the action of the cam a<2>, will vary with the elevation of the sight. The range graduations on the dial A<3> are spaced apart so that the arcuate distance between adjacent graduations (say 1900 yards and 2000 yards) is inversely proportional to the change in range for a given change in muzzle velocity at the lower of the two ranges (1900 yards), from which it follows that any given muzzle velocity correction setting on the reader d<x> will be applicable to all ranges on the dial. The range dial A<3> may be so geared to the cam C that it turns at a faster rate than the cam, in order to enable the range graduations to be opened out. A scale to enable corrections to be made for speed of wind along the line of sight may be interposed between the air density scale e<1> and the speed of target scale e<2>. Two modifications are described embodying the same features as the above, but differently arranged.