mines, at the moment of fire, the distance to which he should direct his gun ahead of its flight, this distance depending on the velocity of the bird's flight and on his distance from it. This manner of shooting is practised the more generally by upland gunners in shooting quail, grouse and woodcock.

The other style of shooting may be designated as "the swing shot," in which the gunner swings his gun ahead of the cross flight of the bird till he attains the proper distance ahead of it, and then fires; but he keeps his gun moving, with a regular angular velocity, till even after its discharge. This method of shooting is, in my opinion and from my experience, the proper method whenever it can be practised, and is certainly the only one which has been found successful in the shooting of bay fowl, as ducks, brant and wild geese. Yet there are sportsmen who will contend that they merely follow the bird with the gun, and discharge it while it is pointing directly at the bird. I put this opinion to the test this summer in the following manner: Four willets came over the decoys flying in line with a good speed. With my gun I followed the first bird coolly and accurately, and kept the gun moving regularly after its discharge. Instead of killing the first bird, the third from the leader dropped dead.

To give a rule applicable to all gunners, for the distance at which a gun should be held ahead of a bird, is not possible. Some sportsmen follow a bird, and then, after reaching before it the proper distance, suddenly stop the angular motion of the gun, and then fire. Others, after following the bird a short distance, give a quick, lateral motion to the gun, and then fire. Others, again, bring the gun, with a lateral motion, ahead of the bird and keep the gun moving till their experience decides the proper distance ahead of its flight, and then fire while the gun is keeping its previous, regular angular velocity.

For the simple illustration of the bearing of these experiments on the art of shooting on the wing, I will suppose that, at the moment of fire, the gun is stationary; in other words, that we are firing "snap shots." If the bird has a velocity across the line of sight of 30 miles an hour (i. e., 44 ft. per sec.), and we are using charges in a 12-gauge gun of 3 1-4 drs. of Curtis & Harvey powder and 1 1-8 oz. of shot, we shall have to shoot about 5 feet ahead of the bird if it is flying at a distance of 30 yards; at 7 feet ahead if at a distance of 40 yards, and 11 feet ahead of the bird if at a distance of 50 yards.

These distances ahead, for cross shots at birds flying at the rate of 30 miles an hour, may appear out of all reason with the experiences of many sportsmen; yet, if you will place a stick 5 foet long at 40 yards, and ask the same gunners if they would hold ahead of a bird by that length, if it were going with a velocity of 30 miles, I venture to say, from my experiments with them, that they will say, "Of course: that is only about 18 inches;" so difficult is it to determine a length at a distance, while sighting along the barrel of a gun.

I will conclude with the remark that the study of this paper will not make a good shot on the wing, any more than a description of how to perform on the violin will make an accomplished violinist. But the results of these experiments are of value, and cannot but improve the shooting of an accomplished sportsman, if they are practically applied.

It has been said, perhaps rather strongly, "reading and writing come of schoolmasters, but a crack shot is the work of God."

APPENDIX.

"A bird at the distance of forty yards is going at full speed (say sixty miles per hour) in a direction perpendicular to the plane of fire; how much shall we hold ahead? It is difficult to find two good shots who will give, even approximately, the same answer to this question; there are those who will say they allow little or nothing, and others who allow from ten to fifteen feet.

It is obvious, that before we can discuss this question to any purpose, we must know approximately the velocity of a charge of shot. It is hoped, therefore, that the following experiments will be of interest to sportsmen.

These experiments were made on the 27th of June last, at the U. S. Naval Experimental Battery at Annapolis, Maryland, with the permission and able assistance of Commander Joseph D. Marvin, U. S. Navy, in charge of the Battery. The instrument used to determine the velocities was a Le Boulangé Chronograph; the gun, which was fired from the shoulder, was a pin-fire breech-loader, No. 12-gauge, thirty-inch barrels, weighing seven and a half pounds.

The chronograph was manipulated, and the observations were taken by Lieut. W. W. Kimball, U. S. Navy, assistant to Commodore Marvin.

The cartridges were not prepared for experimental purposes, but were such as the writer happened to have loaded at the time the experiments were made.

In the table below, H denotes Hazard's Electric Powder, No. 5 grain, and D denotes Dupont's Ducking Powder.

The column headed Range gives the distance between the two screens, one of which was about six inches from the muzzle of the gun.

The velocity given is the mean velocity of the shot between the two screens. When the range is fifty feet, it may be taken as the velocity at 25 feet from the muzzle of the gun; and when the range is 100 feet, at 50 feet from the muzzle.

The first screen consisted of four very fine copper wires placed vertically about half an inch apart; the second screen was about the size of a sheet of common note paper, and was formed of fine copper wire stretched from side to side at intervals of about one-fourth of an inch.

It will be noticed that the charges of powder were somewhat smaller than those commonly used by sportsmen.

If we assume the mean velocity of shot for forty yards to be 800 ft. per second, the time of flight will be 0.115 sec. A bird, flying at the rate of GO miles an hour, goes at the rate of 88 ft. per second, or 13.2 ft. in 0.15 seconds. Again, if we assume the mean velocity of shot for forty yards to be 1,000 ft. per second, the time of flight will be 0.12 seconds, and the distance traversed by the bird, 10.56 ft.

Ducks, when going at full speed, attain a velocity exceeding sixty miles an hour; it would therefore seem that an allowance of 10 or 15 feet, in the case of a duck passing a point under full headway, is not too much, if the distance equals or exceeds 35 yards.

Some successful sportsmen have a habit of making an allowance for the velocity of the bird, by jerking the gun forward at the instant they pull the trigger.

The time which elapses between the instant at which the message which causes the finger to pull the trigger is sent from the brain, and the instant at which the shot leaves the muzzle of the piece, is finite, and doubtless greater than we are apt to suppose. This interval of time probably varies with different individuals; hence arises a larger personal equation. For this and other reasons it is impossible to frame rules which are equally applicable to all sportsmen. Each, if he would shoot well, must make his own rules, which must be carefully modified to accord with his experience and observation. A tolerably accurate knowledge of

the velocity of shot is, notwithstanding, of great service to the thoughtful sportsman.

In these experiments, the time of flight was such as to permit the shot to fall about four inches in going one hundred feet, a distance which is of little importance in comparison with the distance traversed by the bird while the shot is in the air. In the case of most double guns the elevation of the rib at the breech is more than sufficient to compensate for the distance through which the shot will fall in going forty yards. A sight one-tenth of an inch in height, at thirty inches from the eye, will exactly cover a line four inches in length at a distance of one hundred feet. The elevation of the rib of most double guns is greater than one-tenth of an inch." U. S. Naval Academy, July, 1875. J. M. RICE.

[From the "Rod and Gun," July 31, 1875.]

By

A NEW METHOD OF OBTAINING A PERMANENT TRACE OF THE PLANE OF OSCILLATION OF A FOUCAULT-PENDULUM. ALFRED M. MAYER, of Hoboken, N. J.

[ABSTRACT.]

LAST year, in the month of October, I mounted, in the physical laboratory of the Stevens Institute of Technology, a Foucaultpendulum formed of a cannon ball suspended by a steel wire. By floating the ball in mercury, I determined the point on the ball to which the wire should be attached, so that this point and the centre of gravity of the ball should be in the same vertical line. This line, having been prolonged as a diameter of the ball, determined the spot into which I screwed a pointed index. The point of this index, when the ball was stationary, was about 1-40 of an inch above a piece of smoked paper placed on a plate of metal which had been carefully brought into a horizontal plane. The pendulum was now drawn from the vertical by the tension of a delicate cord, one end of which was attached to the ball, the other fastened to a fixed support. The pendulum was started in the usual manner by burning this string. After a few oscillations, a current of electric sparks from an induction coil were passed through the suspending wire, and from the point of the index of

the pendulum through the smoked paper to the metal plate, and thus was obtained a trace of the path of oscillation of the pendulum. At successive and known intervals of time I obtained similar traces, which were rendered permanent by passing the smoked paper through spirit varnish. The intersection of these traces gives the centre around which the angles are measured.

The advantages of the method are: 1st, There is no friction of a tracing point; 2nd, The traces give the centre around which the angles are measured; 3d, The traces are permanent; and 4th, The angles of inclination of the traces can be leisurely and accurately measured.

Last May I described this experiment to Professor Cross of the Massachusetts Institute of Technology, and he then informed me that the same idea had occurred to him, though he had not put it in practice, and also that he had recently mentioned this plan of experimenting before the American Academy of Arts and Sciences in Boston; therefore his name and mine should be always associated in designating this method of obtaining a permanent trace from the Foucault-pendulum.

ON A SIMPLE MEANS OF MEASURING THE ANGLE OF INCLINATION OF THE MIRRORS USED IN FRESNEL'S EXPERIMENT ON THE INTERFERENCE OF LIGHT. By ALFRED M. MAYER, of Hoboken, N. J.

[ABSTRACT.]

THE inclination of the Fresnel mirrors is measured by pasting a disk of known size on a window pane, and then ascertaining the distance at which the disk, when viewed by reflection from the mirrors, appears double and the two disks are tangential to each other. From the known diameter of the disk, and the distance of the disk from the line of intersection of the planes of the mirrors, the angle of inclination of the mirrors is readily calculated.