The age-herald., 1898-07-08
THE FLIGHT
 OF A BULLET
From the Boston Herald.

rom modern guns. The velocity ranges from 1,500 to 5000 feet per second It is computed that the average velocity of the larger guns on the cruiser New York is 2,10O feet per second. To the unlnitiated the way in which this is found out should be of interest.
 In the first place, it may be stated that one cannot time a projectlle as one could horse. Some of them can be seen as they rush through the air. It is a favorte amusement during the battery drill with the old seacoast guns at West Point to stand behind and slightly above the gun, and watch the projectlle from the moment it leaves the muzzle until it strikes the tar- get painted on old Gro Nest mountain, about mile away. Spectators with good eyeslght can also see the shell fired from the large mortar rise to the highest point or It's course, and then descend with rush upon the mountain top q mile and a half away where it bursts into many pieces.
 It is reported that during the recent bom- bardment of Santiago the shells of the cruiser New Orleans could be followed by the eye. This was largely due to the use of smolkeless powder, which permitted clear. vision.
 But in case of smaller projectiles. with greater velocity, it is impossible to see
 
 bo seen or not. it is quite out of the ques- ton to time them enc would race, by simply using the eye and a stop-watch The least hesitation in pushing the spring would make difference of hundreds of feet in the distance travelled Errors such as these would make the results of no practical value.
 Our small arm shoots a bullet only one- third of an inch in diameter, which travels 2,000 feet in second, or a mile in three. It goes so fast that it becomes hot to the touch, due to the resistance of the air which it pushes aside. Strange to say, the heated bullet will cauterize the wound of it's own making, and few of the wounded in our war with Spain will bleed to death unless struck in vital spot.
 The projectile has, beside the forward . velocity, a rotational velocity which is given to it by the riflng of the gun. 9th erwise, since it's length is much greater than it's diameter, it would soon begin to turn end on. The rifng prevents this by causing the bullet to bore a path through tho air, and the higher the forward ve- loclty the higher, too, must be the rota- tional. This turning over and over would destroy the range and the accuracy of the gun.
 The determination of the forward velocity is now made with extreme accuracy. The knowledge of It is of the utmost importance to military science. Various methods have been adopted for its determination within the gun, as well as at various points of the trajectory.
 Two screens, so closely strung with cop- per wire that a projectile in passing on through must break one or more of the strands, are D laced fifty yards apart The wire each screen Is connected with Q battery, which sends a current through 1t, and two instruments, one called disjunc- tor. the other the chronograph Although both circuits pass through these instru- ments, yet they kept distinct and sep- arate.
 The chronograph answers the purpose of a stop-watch of greatest accuracy. Two bars are held up by electric magnets; tho currents flowing in one magnet also flow through it's respective screen, while the current of the other passes through the second screen The disjunctor is an in- strument which is used to break both cir cults at the same instant. As soon as this is done the bars fall, since the eleetro- magnets cease to act when there is no cur rent flowing through them. The bar con- nected with the first screen falls upon a small platfoym, which releases a wedge shaped piece of metal. This strikes the bar connected with the second screen, leav- ing a wedge-shaped slit in it as line Of reference during the experiments.
 This being done, the currents are estab- lished again, and the rods placed once. more under the influence of the electro- magnets. Let a 3.2-inch rife whose muZzle velocity is to be found be placed in front of the first screen. The gun is aimed, fired and it's projectile passes quicker than the roar of the discharge through the first screen, breaking some of it's wires; in an- other instant it Is through the second screen, destroying its electric current, and at last finds resting place in some distant sand pile.
 The break in each circuit Is communicate o5 +a ,.f- of tha Iina inStapilv If tha times at which both occur can be deter mined the problem is solved. For instance, let the time it took to pass over the fifty yards be .075 of second. Then, dividing the by the other, gives 2ooO feet per second as the velocity of the ptojectile.
 The time is found by accurately measur- ing the distance between the first dent, the origin, and the second dent, caused by the projeotie breaking the circuits at dif- ferent times. To illustrate the principle in- volved: If the projectile be of low velocity the distance will be greater than if it trav- eled at high rate of speed, since the first rod would have a longer time to fall before the second starts. If the distance be, say. one inch, then from the law of falling bod les the time for that fall can readily be found, and this will be the time 1t took the projectile to travel over the fifty yards between the screens. Expressed mathemat- ically this law is that the time of the fall is equal to twice the distance of fall di- vided by gravity. Everything in this equal tion Is known after the experiment, eXcept- ing the time, which is readily figured out.
 S, accurate is this determination that the velocity of the swiftest projectile can be found to the fraction of a foot. This means the measurement of time to the thousandth part of a second-a fraction too small to comprehend.
 The trajectory of a projectile is the path it travels, and the way of discovering 1t is simple. Screens are put up in line at ln- tervals of one hundred yards. These are covered with target cloth, and are so built that they can be raised or lowered by ropes running over pulleys, which are in the framework that suppdrts the screens. The refie is put in wise, the muzzle being at the same height as the distant bulls eye. Upon the discharge of the gun the bullet will leave a hole in each screen, and from these it's trajectory is easily deduced and transferred to paper.
 This work is very important, since bull let that rises over a mans head in passing