US656867A

US656867A - Rear sight for firearms.

Info

Publication number: US656867A
Application number: US70699699A
Authority: US
Inventors: Edgar Bronson Tolman
Original assignee: Individual
Current assignee: Individual
Priority date: 1899-02-27
Filing date: 1899-02-27
Publication date: 1900-08-28
Anticipated expiration: 1917-08-28

Description

Patenten Aug 28, |900.

N. A M L T B. rrw.

REAR SIGHT FUR- FIBEARMS.

(Application med Feb. 27, 1899.)

(N Model.)

Elli? NTTED STATES PATENT OFFICEe EDGAR BRONSON TOLMAN, OF CHICAGO, ILLINOIS.

REAR SIGHT Foa FIRE/ARMS.

SPECIFICATION forming part of Letters Patent No. 656,867, dated August 28. 1900;

' Application ined reentry 27,1899. senti No. 706,996. or@ modem To all whom it may concern:

Be it known that I, EDGAR BRoNsoN Tor.- MAN, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Rear Sights for Firearms; and Idohereby declare thatthe following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, and to the letters of reference marked thereon, which form apart of this specification.

Myinvention relates to that class of sights for rilies, small-arms, cannon, or other longrange guns which are placed at or near the breech of such guns and are raised or lowered to compensate for the fall of the projectile at any given range and which are moved laterally to compensate for the lateral deviations of the projectile known as drift and windage.

The objects of my invention are to provide a simple and durable mechanism by which, first, the mere act of elevation or depression of the rear sight, used to compensate for the effect of gravitation upon the flight of the projectile and which is requisite in order that the curved line of Hight of the projectile shall intersect the horizontal (or approximately horizontal) plane inwhich lies the line of the sights of the gun at any given distance from the point of discharge, shall also produce a lateral movement of said sight, which shall compensate for that lateral deflection of the projectile called drift caused in part by the rotation of the projectile upon `its axis, the resistance of the medium through which it takes its flight, thev whip of the barrel of the gun, and other constant and uniform causes, so that'at such given distance the curved line of the flight of the projectile,when said projectile is not affected by wind, shall intersect also the vertical plane in which lie the sights of the gun; second, to enable the marksman to 4maintain the plane which intersects the axis of the bore of the gun and the center of the front sight thereof in a trulyvertical direction with the least possible distraction to the eye at the moment of aiming and firing; third, to quickly and accurately elevate or depress the rear sight and maintain any desired elevation during successive discharges of the gun; fourth, to quickly and `marksman as practicable and to secure the greatest practicable distance between the 'front and the rear sights Without interfering with the breech mechanism of the gun.

When a ride is discharged andtthe projectile passes through the ride-barrel and out upon its flight, it is immediately subjected to and the course of its Hight modified by a number of influences, the more important of which may be enumerated as follows:

First. The law of gravitation draws it toward the earth. To compensate for this influence, it is discharged at a greater or less angle to and above the horizontal plane, according to the distance of its objective.

Second. The air (considered as at rest) is a resisting medium which operates to check its speed. The resistance varies greatly with the velocity of the projectile.

Third. Its revolution upon its longitudinal axis tends to maintain it throughout its Hight in the same angle from the horizontal plane with which it left the gun. Throughout the flight, therefore, there is greater air pressure or friction vupon its lower than upon its upper surfaces, or, testate this fact in other language, there is a partial vacuum behind and above the projectile and a more or less compressed cushion of air before and below the projectile, and upon this compressed cushion of lair the revolving projectile rolls to the right or left of its original line of flight some; what like the action of a billiard-ball when struck by the cue with English, or so as to make what is known as a draw or masse. This lateral deviation of the projectile is usually called drift Fourth. The air, in addition to the retarding influence above referred to when considered as at rest, has another inuence when moving across the line of flight of the projectile. It blows it to the right or left, as the case may be. This lateral deflection of the projectile from its original line of flight is usually termed Windage.7

There are other iniiuences which affect the flight of the projectile. Some of them Vare very obscure, perhaps none more so than the IOO eect of differeutlengths of rifle-barrels (othwise identical) upon the same projectile propelled by the same powder. This probably arises from the differing degree of elasticity of ride-barrels of different lengths, which yield to the stress of discharge with a vibratory motion not yet thoroughly defined, but which may impart a lateral or vertical impulse to the projectile at the instant of leaving the muzzle of the gun. The former is sometimes called whip, the latter jump For the purpose of this explanation the meaning of the term whip will be included in the word drift, which latter word will here be understood to mean' that lateral deflection of the moving projectile from the line of the axis of the bore of the gun produced, occasioned by the revolution of the projectile upon its longitudinal axis and the unequal friction thus produced upon its surfaces by the resisting medium through which it passes, when that medium-the air-is at rest, and also the lateral impulse imparted to the projectile by the vibratory motion of the gunbarrel at the instant of exit, and in short every constant infiuence which uniformly tends to defiect the projectile laterally from the line of the axis of the bore of the gun. The effect of wind upon the Hight of the projectile and the error of the individual marksman are of course excluded from the meaning of the term drift Since the gravitation of the projectile is compensated for by appropriately elevating the rear sight, the drift and windage of the projectile may also .be compensated for by a lateral adjustment of the rear sight, which must be in each case appropriate to the distance, and hence tothe elevation of said rear sight. By any device heretofore used drift has only been approximately compensated for.

In using the expression herein corrections for or graduations to indicate elevation it is to be understood that I mean such an elevation of the eyepiece of the sight as will be necessary to compensate, as aforesaid, for the effect of gravity upon the projectile at a given distance, and in using the term correction for wind or grad uations to correct for Wind I mean to be understood as referring to such location of the eyepiece with respect to the vertical plane of the gun as will compensate for, as aforesaid, the lateral deviation of the projectile due to the action of the wind. I

Myinvention therefore consists in the novel devices and combination of devices herein illustrated and described, and more particularly set forth in the appended claims.

One means of accomplishing the results of my invention consists of a sight-bar having vertical and horizontal members, the latter being provided with a movable eyepiece, with or without a spirit-level and with graduations removably or otherwise affixed thereon to correct for windage, and the former being providedwith graduations to correct for elevation and vertically movable in an appropriate guide, sheath, or frame and in direct or indirect engagement with a Wedge, cam,or other surface, usually affixed directly to the side of the breech mechanism or plate, whereby by the vertical movement of the sight-bar alateral motion is imparted thereto sufficient to automatically correct for drift. In the accompanying drawings I show two forms of mechanismfor producing this lateral deflection; but I desire it to be understood that I am not limited to either of these forms and that any means for automatically producing a lateral defiection of the-sight-bar when the latter is raised or lowered to correct for elevation is comprised within the invention and embraced Within the scope of the claims hercto appended; nor do I desire to be limited, except as indicated herein by specific claims, to the precise details of mechanism for any 'of the features of construction or arrangement illustrated.

In said drawings, Figure l is a side elevation of a rifle equipped with my rear sight attached at the right side of the rifle at its normal or point-blank elevation. Fig. 2 is a transverse vertical sectional view of the same, enlarged, taken upon the line 2 2 of Fig. l, the rear sight being somewhat elevated. Fig. 3 is a plan view of the sight. Fig. 4 is aside elevation of the same with the outer plate or cover removed. Fig. 5 is a transverse vertical sectional view taken upon the line 5 5 of Fig. 4. Fig. 6 is a horizontal sectional view of the sight, taken upon the line 6 f5 of Fig. 4. Figs. 7 and 8 are vertical sectional views taken on the lines 7 7and 8 8, respectively, of Fig. 2,1ookingin the direction indicated bythe arrow. Fig. 9 is a detail View of the spring-dog for locking the sight at any desired elevation. Fig. l0is a vertical sectional View of a modification. Fig. ll is a horizontal sectional view taken upon the line 1l 1l of Fig. lO. Fig. 12 is a plan view of said modification. Figs. 13 and 14 are rear and side views, respectively, of a modified form of the rear sight-piece.

In said drawings, A represents the upright leg or member of the sight-bar, andA the horizontal member thereof. The vertical member is provided, preferably on its rear face, as shown in Figs. 2 and l0, witha scale or graduations to indicate the elevations thereof appropriate to compensate for the fall of the projectile at the range indicated by the figures thereof, which may be expressed in terms of yards, meters, or otherwise, as desired. This member is movably secured in a vertically-arranged guide or frame B, which latter may be fixed with relation tothe stock or lock-plate of the rifie, as indicated in Figs. 2, 3, 4, and 5, or may be hinged or otherwise movably secured thereto, as shown in Figs. l0 and l2.

The sight-bar A may be moved in the guide or frame B by any suitable actuating mechanism. For example, its lower or vertical IOO leg may be slotted and one or both sides of the slot provided with rack-teeth h,'adapted to engage an actuating-wheel H on a shaft h', the latter being operated by a thumb screw or nut h2, or, as shown, one or more pinions H H may be interposed between the rack h and the wheel H. The frictional contact of the sight-bar A in its guide or frame B and of the rack and pinions will usually be sufficient to lock the sight-bar in any desired position during successive shots; but as an additional feature I may use the spring-dog arrangement illustrated in Fig. 9, or I may use a locking-screw H2, as shown in Figs. l

and 3, Where it passes through an interiorlyscrew-threaded aperture in the guide or frame B and engages the sight-bar A, or I may use said screw H2 and said spring-dog b', and it will be manifest also that I may omit the rackand-pinion-actuating mechanism and elevate or lower the sight-bar by hand, simply sliding it in the guide B and then locking it in the desired position by the screw H2,

As an auxiliary or alternative means for determining the elevation of the sight-bar I provide the latter with a plurality of small recesses or notches a, arranged to compensate for the appropriate elevation, and I provide in a suitable recess b in the guide-frame B the spring-actuated dog b', which latter engages the said notches a, as desired. This spring-dog serves the double purpose of frictionally maintaining the sight-bar A in any desired position with respect to the guide B during successive shots and of furnishing means for setting the sight at any desired elevation at night or while the rifle is at the shoulder or while the eye is engaged in watching for the appearance of or gaging the distance of the game or the enemy by merely counting the clicks of the spring-dog as the sight-bar A is moved up or down.

It is well known that the lateral deiiection of the projectile termed drift is not in a right line, but in an increasing and slightlyirregular parabolic curve. To compensate for this drift, I have illustrated two forms of devices. Referring first to that shown in Figs. l to 6, inclusive, C represents a wedge-shaped piece affixed to the side of the lock-plate, stock, or other appropriate part of the ride in any suitable fashion, so that the plane surface nearest the gun-. e. the inner surface-- is parallel to the verticall plane passing through the axis of the bore of the gun and the center tip of the front sight, hereinafter termed for convenience the vertical plane ofthe gun. The outer or opposite plane surface of the wedge C is arranged at an angle to the vertical plane surface thereof equivalent to the average angle of lateral deiiection in the lineof flight of the projectile from the line of the vaxis of the bore of the gun when not affected by the action of the wind-that is to say, when the projectile is affected only by those constant elements which go to make up that effect usually termed drift This average angle is that formed by the right line that most nearly coincides with the irregular or parabolic curve aforesaid. The sight-bar A is arranged so that its vertical member rests against the outer or angular surface of the wedge C, and it will therefore be manifest that when the bar A is raised or lowered to correct for elevation an automatic correction for drift takes place, inasmuch as the horizontal member A of said bar which carries the rear sight is moved laterally toward or from the vertical plane of the gun. In most forms of rifie this wedge-plate C will be found sufliciently accurate for all practical purposes. Applied to guns in which the drift is to the left of the line of the axis of the bore the wedge C will be affixed to the right side of the lock-plate, stock, or other appropriate portion of the gun with the larger or thicker end upward, as shown in Figs. 2 and 5, so that as the vertical leg or member of the sight-bar A is elevated it will also be automatically carried laterally to the right of the line of the axis of the bore. Applied to guns in which the drift is to the right the wedge will be similarly affixed to the right side of the gun, but with the larger or thicker end downward. The wedge of course may be affixed to the other side of the gun; but I prefer to place it on the right side, as shown, on account of the greater handiness in manipulating the sight. As clearly shown in Figs. 3 and 6, the wedge C is made separate from the guide B and may or not be attached to the side of the gun by the same means which fixes the guide in place. `With this construction said wedge may be used interchangeably with different guns having right and left drift, and said wedges may be used interchangeably with different guides. Moreover, said wedge may be easily and readily attached to certain sight mechanisms wherein provision was originally made for compensating for distance only or Where the sight-bar had originally only vertical movement.

The horizontal arm A' of the sight is fixed at such an angle to the vert-ical leg or member thereof as to bring said horizontal arm at right angles to the vertical plane of the gun land to the inner plane surface of the wedge C. This is a detail of prime importance, for the reason that in shooting at long range with the rear sight elevated if the sight is tipped to the right or left the projectile will go to the right or left, respectively, of the line of sight. It is therefore essential to` provide means of maintaining the vertical plane of the gun in a true perpendicular, which may be done by the practiced eye by holding the rifle so that this lateral member A is horizontal or by means of a spirit-level so adjusted as to be in a horizontal plane parallel to that of the arm. This lateral member A carries an eyepiece D, usually termed rear sight, of any familiar construction, comprising a small metal block with a peep or sight aperture d and lateral grooves or recesses d', which lat- ICO ter are adapted to dt within and be engaged by the side walls d2 of an elongated slot d3 in said horizontal member A. A screwD', provided with a thumb-piece d'1, is rotatably mounted in said slotted opening d3 and passes through and engages the eyepiece l), whereby by the rotation of said screw D the eyepiece D may be moved lengthwise of the arm A in said slot, the recesses CZ and walls d2 affording suitable bearings and guides for the same. Upon the upper face of the horizontal member A' may be afiixed the usual graduations or scale to indicate windage. I prefer, however, that the scale or graduations shall be so arranged that the smallest unit will indicate the necessary correction of the sight in tiring at an object one hundred (100) yards distant for the effect of a cross77 wind-t. c., a wind blowing at right angles to the line of lire with a velocity of one mile per hourso that the necessary compensation for different ranges and winds of different velocities may be more easily made. I prefer, however, to mark these graduations upon a removable plate D2, securing the latter to the arm A by means of screws d5 passing through elongated slots or openings d in said plate D2. The advantage of the slotted opening d is thatit enables me to accurately adjust the center of the windage-scale to com pensate for the irregularities or peculiarities in the construction of rifles of different makes or of differences in the same make of rifles. Of course it will be understood that when the plate D2 is once applied it will remain in position upon the horizontal member A.

As a separate improvement I attach a spiritlevel E to the eyepiece D in such manner that the normal center of the spirit-level will be directly under the center of the eyepiece when the arm A is horizontal. I therefore movably secure the spirit-level E to the said eyepiece, and this may be done in several ways. In Figs. 2, 7, and 8 I illustrate one way of securing the spirit-level in position-namely, by a recess e, bored into said eyepiece near its lower end, but so close to the rear face thereof as to intersect the latter,and thus provide an elongated slot e in said rearsurface, through which slot the spirit-level when inserted in said slot will be visible from the rear, as shown in Fig. 2. Any form of spiritlevel may be inserted in said recess e and removably secured therein by a pivoted locking-cap e2. I prefer, however, to insert the spirit-level E in the recess e and secure the same in position by means of an adjusting screw-threaded plug c3 and in terpose a spring e4 between the inner end of said recess and said spirit-level, as shown more clearly in Figs. Il and l2. By this latter arrangement I am enabled not onlyto hold the spirit-level in position, but also to accurately adjust the same whenever required to do so. I have shown the recess e located both above and below the side grooves d in the eyepiece, the exact location not being material, excepting that in military rifles I prefer to locate the spirit-level as indicated in Figs. 7 and 8-to wit, below the horizontal member A of the sight-bar-thus thereby affording better protection from breakage. The central point of the spirit-level may be indicated by a mark on the rear face of the eyepiece or sight D, and whenever the bubble is at this mark-that is, directly under the center of the sight aperture or notch of said eyepiece D-the vertical plane of the gun will be in a true perpendicular position.

I have already stated that the automatic correction for drift secured by my device, as above described, is an average or approximate correction and will be found sufiiciently accurate for all practical purposes in guns having a normal or regularly-increasing drift at increased ranges; but Figs. lO, l1, 12, and 13 show a modification of my invention, which affords a mathematically-exact correction for drift and all other lateral deflections of the the projectile caused by constant forces peculiar to the gun and the resistance of the air other than the effect of wind or the error of the marksman. I have taken, for example, the somewhat-erratic course of the .S0-caliber bullet with service-charge of smokeless powder fired from the Krag-Jorgensen gun of the present model, as stated in the United States Grdnance Department reports for the year ending ISQS. Assuming the tables therein stated to be correct, the rear sight requires a IOO greater lateral correction to overcome drift I at one hundred yards than at two hundred. It decreases irregularly from one hundred to four hundred yards, then increases irregularly to one thousand yards, and then decreases irregularly to seventeen hundred yards, increasing slightly at eighteen hundred yards, at which range the table stops. Now it is evident that if this table is correct there are eccentricities ofthe gun or projectile, or both, affecting the result which do not exist in other rifles-say, for example, the Springfield military riiie. These constant eccentricities of any arm, so far as they affect lateral deviations of the projectile from the line of the axis of the bore produced, can be automatically corrected7 and therefore disregarded by the marksman, by applying the principles of my invention as illustrated in the modification now about to be described.

In Fig. IO, F indicates a part similar in function to the wedge A, Fig. 2, and provided with an exterior cam-surface f, curved and graduated so as to correspond with the irregular curve of the bullet laterallyfrom the axis of the bore. Upon this curved or cam-face f the upright leg A of the sight-arm rests at single point only, preferably by means of the stud f', affixed to the leg A. The stud f will usually be positioned near the bottom of the leg A and will be of such length as to clear the leg A and the movable guide or frame B from the thickest part of the cam F when said stud f is resting upon said cam at its thin- IIO nest point. As the stud f rises with the leg lA a sufficient distance to compensate for the bears will be sufficient to exactly compensate for the known drift or constant lateral delicotion of the bullet at that distance and so at each point of elevation.

The guide or frame B may be movably secured to the riiie in any convenient manner; but the means herein illustrated (see Fig. l0) comprises links or arms G, preferably two on each side of the guide, pivotally secured at one end to the rifie and at the other to the guide, whereby a lateral and vertical movement may be imparted to the guide B, and the latter will always be in a plane parallel to the vertical plane of the gun. In this form of sight the elevation-scale may either be on the leg A, as already shown, in which case it should be graded to allow for the vertical lnovement of the guide or frame B, or it may be on the face of the wedgeoid or cam F and traversed by and read from the stud f.

In Figs. 13 and 14 I have shown the sightpiece D in that form known as an open sight. Instead of the circular' aperture or peep d I provide a horizontal portion with a semicircular recess or notch C17. -The top of the eyepiece D is tapered to a knife-edge, as shown in Fig. I4. This is a familiar form of rear sight.

What I claim as my invention, and desire to secure by Letters Patent, is as follows:

l. A rear sight for firearms, comprising a guideadapted to be attached to the side of the gun, a sight-bar engaging the guide and provided at its upper end with an arm adapted to project laterally above the level of the barrel of the gun to which the sight is attached, an eyepiece on said arm, and a part having an inclined surface adapted to be affixed to the side of the gun,`between the gun and sight-bar, and engaging said sight-bar, whereby when the sight-bar is being elevated or depressed the eyepiece will be caused to move laterally with respect to the vertical plane of the axis of the gun-barrel.

2. A rear sight for firearms, comprising a guide adapted to be attached to the side of the gun, a sight-bar engaging the same and provided at its upper end with a lateral arm adapted to project over the gun-barrel, an eyepiece on said arm, and a part adapted to be attached to the said gunbetween the sightbar and the gun and separable from the guide, said part being provided with an inclined surface engaging the sight-bar.

3. A rear sight for firearms, comprising a sight-bar which is capable of being elevated or depressed and which carries at its upper end an eyepiece, a guide therefor, and means connected with the guide for laterally deflecting the eyepiece when the sight-bar is being elevated or depressed, said deflecting means being capable of assu ming two positions in the guide, whereby the device may be used on either side of the gun and for guns having right or left drift.

4. A rear sight for firearms, comprising a vertically-movable sight-bar carrying an eyepiece at its upper end, a guide for said bar and a part having an inclined surface engaging said bar, said part being reversible, Whereby the eyepiece may be moved laterally, past either side of the plane of the gun when the bar is being elevated or depressed.

5. A rear sight for firearms, embracing a sight-bar adapted to be secured to the side of the gun and provided at its upper end with an arm which is adapted to project over'the gun-barrel, an eyepiece on said arm, and a reversible part having an inclined surface adapted to be affixed to the side of the gun and engaging said sight-bar, whereby when the sightbar is being elevated or depressed the upper end thereof will be caused to move laterally with respect to the vertical plane of the axis of the gun-barrel.

6. A rear sight for firearms, comprising a vertically-movable sight-bar carrying an eyepiece at its upper end, a vertical guide for said bar, and a reversible part which is made separate from said guide and which is provided with an inclined surface adapted for engagement with said sight-bar. y

7. A rear sight for firearms, comprising a vertically-movable sight-bar, a vertical guide therefor, a reversible part which is made separate from said guide which is provided with an inclined surface adapted for engagement IOO with said sight-bar, a lateral arm on the upper end of said sight-bar, and an eyepiece movably affixed to said arm.

8. A rear sight for firearms, comprising a sight-barwhich is capable of being depressed and elevated, an eyepiece carried bythe upper end thereof', and a part engaging said si ght-bar with respect to which the sight-bar` is movable and which is irregularly shaped to correspond with the laterally-d eiiected path of the projectile due to drift and like constant causes, whereby when the sight-bar is elevated or depressed the eyepiece is moved laterally in an irregularly-curved path with respect to the vertical plane of the axis of the gun-barrel, to compensate for drift 9. A rear sight for firearms, comprising a sight-bar whichis capable of being depressed and elevated, a horizontal arm on the upper end of said bar which projects laterally over the gun-barrel, an eyepiece carried by said arm, and a part engaging said sight-bar, with respect to which the sight-bar is movable and which is irregularly shaped to correspond with the laterally-deflected path of the projectile due to drift and like constant causes, whereby when the sight-bar is elevated or depressed the eyepiece is moved laterally in an irregularly-curved path with respect to the vertical plane of the axis of' the gun-barrel to compensate for drift.

10. A rear sight for firearms, comprising a vrI Io vertically-movable' sight-bar, a guide therefor adapted to be attached to the side of the gun, a part having an inclined surface associated with, said guide which is located between the bar and the gun and engagingsaid sight-bar, a lateral arm on the upper end of the bar, and an eyepiece movable laterally on said arm, said arm being disposed at such angle to the sight-bar as to be at right angles to the vertical plane which intersects the axis of the bore of the gun-barrel and the center of the front sight, so as to enable the marksman to plumb his gun.

1l. A rear sight for firearms, comprisinga vertically-movable sight-bar adapted to be attached to the side of the gun, a vertical guide therefor, a part having an inclined surface associated with the guide which is 1ocated between the bar and the gun and engaging said sight-bar, a lateral arm on the upper end of the bar, an eyepiece movable on said arm, said arm being disposed at such angle to the sight-bar as to be at right angles to the vertical plane which intersects the laxis of the bore of the gun-barrel and the center of the front sight, and a spirit-level secured to and movable with said eyepiece.

l2. A rear sight for a rille comprising a horizontal member, an eyepiece movable thereon, a recess in said eyepiece, an elongated opening` through the rear Wall of said recess, a spirit-level located in said recess, a spr-ing in said recess against which one end of the spirit-level rests, and a screw-plug closing the other end of said recess whereby said spirit-level may be centered or adjusted, and also held removably in Aposition in said recess.

13; The combination With a horizontal sight-arm, of an eyepiece movable laterally on the arm and having a sight notch or aperture, and a spirit-level connected with said `eyepiece below said sight-notch so as to move the plane which intersects the axis ofthe bore of the gun-barrel and the center of thev 14E. A rear sight for firearms comprising a part having an inclined surface secured to the rifle, a guide movably secured to the rifle, a sight-bar the vertical member of which is 'adapted to move in said guide and which is deflected laterally by said part and means for actuating the sight-bar whereby the curved line of ilight of the projectile when not aected by the Wind is caused to intersect the line of sight of the gun at any desired distance.

15. A rear sight for a rifle comprising a vertical and a horizontal member, the latter being provided with graduations to correct for lateral deviation due to Wind, with an eyepiece movably secured thereto and with a spirit-level removably and adjustably secured to the eyepiece, the vertical member being provided with graduations to correct for elevation, a guide movably mounted at the side of the rifle and adapted for the vertical movement of the sight-bar therein, a cam-surface on the rifle, means for engaging the vertical member of the sight-bar with l said cam-surface whereby the vertical adjustment of the sight-bar to correct for elevation at a given range will automatically and simultaneously cause the curved line of ilight of the projectile When not affected by Wind to intersect the line of sight of the gun at such distance, thereby correctin g fordrift, substantially as described.

In testimony that I claim the foregoing as my invention I aiiiX my signature,in presence of two witnesses, this 2 lst day of February, A. D. 1899.

EDGAR BRONSON TOLMAN.

Witn esses:

TAYLOR E. BROWN, CHARLES W. HILLS.