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UF145 .B47"'l875™""'' '""'"'^ \vwimS, oxygen easily, and makes a powder, which has beei WATUEE OF CHAECOAL. 15 found by experience, to give at least double the range with the mortar eprouvette, of that made with nitrate of potassa, but from its great quickness, resembles the fulminates in its destructive effects on the gun. Besides, it is more costly than nitrate of potassa, renders the powder liable to explode by slight causes, and gives a residue which rapidly corrodes iron. Its use in the laboratory is chiefly confined to the preparation of colored fires and cannon primers. The nitrate of soda is found as an extensive deposit in the soils of some portions of Peru and northern Mexico. It is cheaper than nitrate of potassa, and for the same weight affords a greater amount of nitric acid, or oxygen. Its affinity for moisture constitutes a serious objection to its use in the manufacture of a gunpowder for war purposes, or one that is to be preserved for any length of time. The nitrate of soda may be used in obtaining the nitrate of potassa by decomposing it with carbonate of potassa — ^the potash of commerce. CHAECOAL. 7. Mature of charcoal. Charcoal is the result of the incomplete combustion or distillation of wood. Its composition and properties vary with the nature of the wood, and mode of distillation employed. Charcoal obtained from light wood is the best for gunpowder, as it is more combustible and easy to pul- verize, and contains less earthy matters. Willow and poplar are used for this purpose in the United States, and the black alder in Europe. The wood must be sound, and should not be more than three 1 6 GUNPOWDER. CHARCOAL. or four years old, and about one inch in diameter; branches larger than this should be split up. It is cut in the spring, when the sap runs freely, and is imme" diately stripped of its bark. The smaller branches are used for fine sporting powder. The operation of charring may be perfonned in pits, but the method now almost universally used' in making charcoal for gunpowder is that of distillation. For this purpose the wood is placed in an iron vessel, generally of a cylindrical form, to which a cover is luted; an opening with a pipe is made to conduct off the gaseous products, and the wood is thus exposed to the heat of a furnace. The progress of distillation is judged of by the color of the flame and smoke, and sometimes by test-sticke,yflin(^ are introduced through tubes prepared for the purpose. 8. Properties. The charcoal thus obtained should retain a certain degree of elasticity, and should have a brown color, the wood not being entirely decomposed ; it retains the fibrous appearance of the wood, and the fracture is iridescent. As it readily absorbs l-20th of its weight of moisture, which diminishes its inflam- mability, it should be made only in proportion as it is required for use. "Wood generally contains 52 per cent, of carbon, but distillation furnishes not more than 30 to 40 per cent, of charcoal. The specific gravity of charcoal triturated under heavy rollers, is about 1.380 ; but in sticks, as it comes from the charring cylinders, it rarely exceeds .300. The properties of charcoal vary much with the temperature employed in the preparation. If wood be merely heated until it ceases to give off vapor, a true ACCIDENTS. n charcoal is obtained ; but by raising tlie temperature to redness or whiteness, its properties will be much changed, as is shown in the following table : When not heated to rednes3. Heated to redness. Heated to whiteness. For electricity, " heat. Combustibility, Non-conductor. Very bad conductor. Easy. Good conductor. Good conductor. Less easy. Excellent conductor. Excellent conductor. Difficult. If sufficient heat be applied to drive off all the vola- tile matters in six hours, a black charcoal, containing from 28 to 33 per cent, of carbon, will be obtained. If the heat be reduced so as to prolong the distillation to twelve hours, the charcoal will have a yellowish brown color, and will contain from 38 to 40 per cent, of car- bon. Charcoal inflames at about 460° Fahrenheit. A black coal strongly calcined takes fire quickly, but is .easily extinguished. A brown charcoal takes fire slowly, but burns strongly and rapidly. As it is desir- able to have charcoal for gunpowder very combustible, it must therefore be prepared at a low temperature, and must be light. In distillation, the heat is kept below redness. 9. Accidents. When recently prepared charcoal is pulverized and laid in heaps, it is liable to absorb oxy- gen with such rapidity as to cause spontaneous combus- tion. This has been the cause of serious accidents at powder-mills; and hence it is important not to pul- verize charcoal until it has been exposed to the air for several days. In Prussian powder-mills, pulverized 18 GUNPOWDEE. GHAECOAL. charcoal is kept in a fireproof room, in iron vessels, as a precaution against accidents. When charcoal has not absorbed moisture, and is mixed with oxydizing substances, it may be inflamed by violent shocks, or by friction. This is the principal cause of the accidents which occur in the preparation of explosive mixtures which contain charcoal. 10. CombMstibiiity. For the purpose of comparing the combustibility of charcoals made of different mate- rials, a certain quantity of each is thoroughly mixed with nitre, in the proportion of 1 part of the former to 5 of the latter, and driven compactly into an ii'on tube about .25 inches in diameter; the weight and length of the filled tube are taken, and the duration of the com- bustion is ascertained by a pendulum or chronometer. The length of composition burned in a second of time is called the velocity of combustion, and is taken as the measure of the combustibility of that particular kind of charcoal. The amount of residue is ascertained by subtracting the weight of the tube and residue after burning from that of the filled tube before burnins;, and again subtracting this difference from the weight of the composition originally in the tube. The velocity of combustion is independent of the diameter of the tube and of the material of which it is made ; but it varies slightly with the j)ressure used in driviuo- the composition, and very much with the degree of tritura- tion of the materials. The following tables contain some of the results thus obtained, viz. : COMBUSTIBILITY OF CHAECOAL. 19 60 parts of nitre and 12 of charcoal. Velocity o room- Percentage of Black Charcoals. bustic n. residue. Charcoal of Hemp, .31 in ch. 16.6 t ' Grape Vine, . .26 ' 27.7 I ' Pine, . .18 ' ' 41.6 I Black Alder, . .16 ' ' 33.3 I ' Spindle Tree, .15 ' ' 87.5 ' ' Hazel, . .13 ' 41.6 ( ' Chestnut, . .14 ' ' 50.0 I Walnut, .11 ' 45.8 i Coke. .06 ' 62.5 t Sugar, . .04 ' ' 66.6 Charcoal made by distilling Black Alder, and conducted so as to give, For 1 00 p'ts wood, 40 p'ts charcoal, .14 in ch. 39.0 " " 30 " .16 " 37.0 " " 25 " .15 " 33.3 11 (t 15 i< .12 ' 35.0 The following table shows tlie influence of trituration and proportion of ingredients : Mixture. Parts of charcoal til CO of nitre. Charcoal made of Hemp. Charcoill made of Pine. 6 hours' trituration. 4 hours' trituration. 6 hours' trituration. 4 hunrs^ tritur.atioli. Telocity. Per ct. of residue. Velocity. Pr. ct of residue. Velocity. Velocity. i i i i- i 8^ 10 12 15 20 30 60 .10 in. .12 .HI .39 .56 .65 .14 58.0 45.0 16.6 13.0 12.0 11.0 .08 in. .10 .17 .27 55.0 43.0 26.0 17.0 .09 in. .15 .18 .35 .39 .59 .07 in. .09 .12 .20 .27 .53 20 GUNPOWDEK. SULPHUE. SXJLPHUE. 11. Properties. Pure sulpliur is of a citron-yellow color, and shining fracture ; it crackles when pressed in the hand. The specific gravity of native sulphur is 2.033; that of sulphur refined by sublimation 1.900; its specific gravity is diminished by trituration. When heated, it melts at 226° into a thin, amber-colored liquid; if the temperature be then raised to about 400" it be- comes dark and thick; but if heated still further, up to 800", its boiling point, it becomes again thin and limpid. It begins to pass off in vapor at 115°, and if heated rapidly, inflames at 370°. It is insoluble in water, but soluble in oils and slightly so in alcohol. Sulphur is generally found in great quantities in the neighborhood of volcanoes; it may also be obtained from metallic ores (pyrites) and other sources. Most of that used in the United States comes from Sicil}- through the French refineries. Crude sulphur, as extracted by the first sublimation from the ore, contains about 8 per cent, of earthy mat- ter. It is purified by a second sublimation, from which it is collected in the form of powder, called the fiotoers of sulpliur; or, it is melted and run into moulds, mak- ing roll brimstone. It may be also refined, but not so thoroughly, by being simply melted and skimmed. Pure sulphur is entirely consumed in combustion; and its purity is thus easily tested by burning about 100 grains in a glass vessel; the residue should not ex- ceed a small fraction of a grain. MANUFACTUEE. 21 MANUFACTUEE OF GUNPOWDEK. 12. ProportioEis of ingredients. Nitre. Charcoal. Sulphur By the atomic theory, .^ . 74.64 13.51 11.85 In the United States: For military service, . . . 76.00 14.00 10.00 For "blasting and mining, . 62.00 18.00 20.00 The proportions of the ingredients of the earliest gunpowder known, differ hut slightly from those now in use; and these, it will be seen,* nearly agree with those called for by the theory of combining equivalents. For the general purposes of artillery, slight varia- tions in the proportions of the ingredients for jDowder are not found to affect its strength; but for blasting or mining purposes, a slower powder is found to answer nearly as well as a quick one, consequently the propor- tion of nitre is reduced much below that of gunpowder. Blasting powder is thus made cheap; but as it leaves a large amount of residuum, it cannot be advantageously used in fire-arms. 13. Operations. The several operations of fabrica- ting gunpowder are: 1st. Ptol/uerizing ; which consists in reducing the ingredients to finely divided dust. 2d. Incorporating; which consists in bringing the particles of this dust into such intimate contact that each particle of powder shall be composed of one of each of the ingredients. 3d. Compressing ; which gives strength and density to the substance of the powder, by converting the in- 22 GUNPOWDER. MAWTTFACTUEE. corporated mixture into a cake which will not crumble in transportation. 4th. Graining ; which breaks up the cake into small fragments or grains, and increases the surface of com- bustion. 5th. Glazing ; Avhich hardens the surface, to protect it from the action of moisture, and rounds the sharp angles of the grains to prevent the formation of dust in transportation. 6th. Drying • which frees the powder from the moistiu^e introduced in certain operations of the fabri- cation. Tth. Dusting I which frees it from the dust, which would otherwise fill up the interstices and retard the inflammation of the charge. The j)roportions of the ingredients, as well as the art of making gunpowder, vary in different countries, and even among the different manufactories of the same country. The variations in the proportions are slight, how- ever, and the differences in the modes of manufacture are principally confined to the more important opera- tions of pulverizing, mixing, and compressing the com- position. For French military powder, these operations are performed in the "pounding-mill," or a series of mortars and pestles. In Prussia the composition ' is pressed into cake by passing it between two heavy rol- lers, by means of an endless band of cloth, Avhich re- ceives the dust from a hopper. In England these operations are performed by the "rolling-barrel," "cyl- inder-mill," and "press." The superior strength and excellent preservative qualities of the English powder MANUFACTTJEE. 23 have led to the adoption of this mode of manufacture in the United States. 14. Processes of mannfactnre.'^ The buildings in Avliicli tlie different operations are carried on are sepa- rated from each other, and protected by trees or trav- erses as far as practicable. Pulverizing. The saltpetre is usually pulverized sufficiently when it comes from the refinery. The, char- coal is placed in large cast-iron barrels with twice its weight of zinc balls. The barrel has several ledges on the interior, and is made to revolve from 20 to 25 times in a minute. It is pulverized in 2 or 3 hours. The sulphur is placed in barrels made of thick leather stretched over a wooden frame, with tAvice its weight of zinc balls from .3 to .5 inches in diameter, and the barrel made to revolve about 20 times per minute. It takes one hour to pulverize the sulphur. Incorporating. The ingredients having been weigh- ed out in the proportions above given, the charcoal and sulphur are put together in a rolling-barrel simUar to that in which the sulphur is pulverized, and rolled for one hour. The saltpetre is then added, and rolled for three hours longer. In some mills this operation is omitted. It is now taken to the cylinder, or rolling- mill. This consists of two cast-iron cylinders rolling I'ound a horizontal axis in a circular trough of about 4 feet diameter, with a cast-iron bottom. The cylinders are 6 feet in diameter, 18 inches thick on the face, and weigh about 8 tons each. They are followed by a wooden scraper, which keeps the composition in the centre of the trough. * Vide Ordnance Manual 24 GUKPOWDEB. MAKUFACTUKE. A charge of Y5 lbs. in some mills, and 150 lbs. m others, is then spread in the trough of the rolling-mill, and moistened with 2 to 3 per cent, of water, according to the hygrometric state of the atmosphere. It is rolled slowly at first, and afterward from 8 to 10 revolutions of the roller per minute, for 1 hour for 50 lbs., and 3 hours for 150 lbs. of composition. A little water is added, as the process advances, if the composition gets very dry — which is judged of by its color. When the materials are thoroughly incorporated, the cake is of a uniform, lively, grayish, dark color. In this state it is called miU-cdke. The quality of the powder depends much on the thorough incorporation of the materials, and burns more rapidly as this operation is more thoroughly per- formed. The mill-cake is next taken to the press-house, to be pressed into a hard cake. Pressing. The mill-cake is sprinkled with about 3 per cent, of water, and arranged in a series of layers about 4 inches thick, separated by brass plates. A pow- erful pressure is brought to bear on the layers, which are subjected to the maximum pressure for about 10 to 15 minutes, when it is removed. Each layer is thus formed into a hard cake about an inch thick. Granulating. The cake is broken into pieces by means of iron-toothed rollers revolving in opposite directions, their axes being parallel and the distance between them regulated as required. Fluted rollers are sometimes used. The pieces are passed through a succession of rollers, each series being closer together, by which the pieces MANUFACTURE. 25 are broken into others still smaller, whicli pass over a sieve to another roller, the small grains passing througli the sieve into a receiver Ibelow, until the whole is re- duced to the required size. The various-sized grains are separated by the sieves between the different rollers. Glazinj. Several hundred pounds of the grained powder, containing from 3 to 4 per cent, of water, are placed in the glazing barrel, which is made to re- volve from 9 to 10 times per minute, and in some mills from 25 to 30 times per minute. Usually from 10 to 12 hours are required to give the required glazing. In this operation the sharp angles are broken off, there- by diminishing the dust produced in transportation, and the surface of the grain receives a bright polish. Drying. The powder is spread out on sheets stretch- ed upon frames in a room raised to a temperature of 140° to 180° by steam-pipes or by a furnace. The tem- perature should be raised gradually, and should not exceed 180", ventilation being kept up. Dusting. The powder is finally sifted through fine sieves, to remove all dust and fine grains. 15. RoHud powder. In case of emergency, and when powder cannot be procured from the mills, it may be made, in a simple and expeditious manner, as fol- lows: Fix a powder-barrel on a shaft passing through its two heads, the barrel having ledges on the inside; to prevent leakage, cover it with a close canvas glued on, and put the hoops over the canvas. Put into the barrel 10 lbs. of sulphur in lumps, and 10 lbs. of charcoal, with 60 lbs. of zinc balls or of small shot (down to No. 4, 0.014 in. in diameter nearly); turn it, by hand or otherwise, 30 revolutions in a minute. 26 GTJNPOWDEK. ^MANUFACTURE. To 10 lbs. of this mixture thus pulverized, add 30 lbs. of nitre, and work it two hours with the balls ; water the 40 lbs. of composition with 2 quarts of water, mixing it equally with the hands, and granulate with the graining-sieve. The grains thus made, not being pressed, are too soft. To make them hard, put them into a barrel having 5 or 6 ledges projecting about 0.4 in. inside ; give it at first 8 revolutions in a min- ute, increasing gradually to 20. The compression will be j)roportionate to the charge in the barrel, Avhich should not, however, be more than half full ; continue this ojDeration until the density is such that a cubic foot of the powder shall weigh 855 oz., the mean den- sity of round jjowder ; strike on the staves of the bar- rel from time to time, to prevent the adhesion of the powder. Sift the grains and dry the powder as usual. That which is too fine or too coarse is returned to the pulver- izing-barrel. This powder is round, and the grain is sufficiently hard on the surface, but the interior is soft, which makes it imfit for keeping, and may cause it to burn slowly. This defect may be remedied by making the grains at first very small, and by rolling them on a sheet or in a barrel, watering them from time to time, and adding pulverized composition in small proportions ; in this way, the grains will be formed by successive layers ; they are then separated according to size, glazed and dried. It appears from experiments that the simple incorpo- ration of the materials makes a powder which gives nearly as high ranges with cannon as grained powder. INSPECTION, PKOOF, ETC. 27 The incorporated dust from the rolling-barrel may be used in case of necessity. INSPECTION, PEOOF, ETC. 16. Proving powder. Before powder for the mili- tary service is received from the manufacturei-, it is inspected and proved. For this purpose, at least 50 barrels are thoroughly mixed together. One barrel of this is proved by firing three rounds from a musket, with service-charge, if it be musket powder ; if cannon or mammoth powder, from an 8-iuch columbiad, with 10 lbs. and a solid shot of 65 lbs. weight and 7.88 inches in diameter; if it be mortar powder, from a 3-inch rifle- gun, with a charge of 1 lb. of powder and an expand- ing projectile weighing 10 lbs. The general character of the grain, and its freedom from dust, are noted. General qualities. Gunpowder should be of an even- sized grain, angular and irregular in form, without sharp corners, and very hard. When new, it should leave no trace of dust when poured on the back of the hand, and when flashed in quantities of 10 grains on a copper plate, it should leave no bead or foulness. It should give the required initial velocity to the ball, and not more than the maximum pressure on the gun, and should absorb but little moisture from the air. Size of grain. There are five kinds of powder in the U. S. land service, depending on the size of the grain, viz.: Mammoth ioY the 15-inch gun. Cannon iov small- er sea-coast guns and mortars, Mortar for field and siege cannon, Mu-sket for rifle-muskets, and Rifle for pistols. 28 GITNPOWDEE. INSPEOTIOW, ETC. The size of the grain is tested by standard sieves made of sheet brass pierced with round holes. The diameters of the large and small holes are as fol- lows, viz.: For Mammoth, 0.9 inch and 0.6 inch ; for Cannon, 0.31 inch and 0.27 inch; for Mortar, 0.1 inch and 0.07 inch; for Musket, 0.06 inch and 0.035 inch. Not more than 5 per cent, should I'emain on the lai-ge, nor pass through the small standard sieves. Gravimetric density. Is the weight of a given meas- ured quantity. It is usually expressed by the weight of a cubic foot in ounces. This cannot be relied upon for the true density when accuracy is desired, as the shape of the grain may make the denser powder seem the lighter. Specific gra/oity. The specific gravity of gunpow- der must be not less than 1.75 ; and it is important that it should be determined with accuracy. Alcohol and water saturated with saltpetre have been used for this purpose ; but they do not furnish accurate results. Mercury, only, is to be relied upon. Merciory deivsimeter. This apparatus was invented by Colonel Mallet, of the French army, and M. Bianchi, and consists of an open vessel containing mercury, a frame supporting a glass globe communicating by a tube with the mercury in the open vessel, and joined at top to a graduated glass tube, which commimi- cates by a flexilole tube with an ordinary air-pump. Stop-cocks are inserted in the tubes above and below the glass globe, and a diaphragm of chamois-skin is placed over the orifice at the bottom of the glolie, and one of wire-cloth over the upper orifice. INSPECTION, PEOOP, ETC. 29 The operation consists as follows: Fill the globe witL. mercury to any mark of tlie graduated tube, by means of tlie air-pump ; close tlie stop-cocks ; detach the globe, full of mercury, and weigh it; empty and clean the globe; introduce into it a given weight of gunpowder ; attach the globe to the tubes ; exhaust the air till the mercury fills the globe and rises to the same height as before; shut the stop-cocks; take off the globe and weigh it as before. If we represent by a the weight of the powder in the globe, by P the Aveight of the globe full of mercury, by P' the weight of the globe containing the powder and mer- cury, and by Z> the specific gravity of the mercury. The specific gravities of the powder and the mer- cury being proportional to the weights of equal volumes of these two substances, we have a:P-P'^a: : d : B ■, 7 axP hence «=-i-; — ^^ P.-P'+a A mean of three results will give the true specific gravity. If the powder is good in other respects, the density may vary from 1.67 to 1.79. Initial velocity. The initial velocity is determined by the Electro-Ballistic Pendulum. It should not be less than 1,050 feet for Mammoth, 1,225 feet for Can- non, 1,000 feet for Mortar and 975 feet for Musket powder. Strain on the gun. The strain on the gun is de- termined by Major E,odman's pressure-j)iston, an in- strument which is attached to the breech of the proof gun, and the principles of Avhich are explained on page 152. 30 GUICPOWDEE. INSPECTIOJT, ETC. For Mammotli powder the pressure should not be more than 10,000 lbs., for Cannon, not more than 40,000 lbs., and for Mortar not more than 50,000 lbs. to the square inch. Infection report. The report of inspection should show iihQ place and date of fabrication and of proof, the hind of powder and its general qualities, as the number of grains in 100 grs., whether bard or soft, round or an- gular, of uniform or irregular size, and if free from dust or not ; the initial velocities obtained in eacli fire ; the amount of moisture absorbed ; and, finally, the height of the barometer and hygrometer at the time of proof. 17. Packimg. Government powder is packed in bar- rels of 100 lbs. each. The barrels are made of Avell- seasoned white oak ; and hooped with, hickory or ceda]" hoops, which should be deprived of their bark to ren- der them less liable to be attacked by worms. Barrels made of corrugated tin are undergoing trial, to test their fitness to replace those made of wood. Marhs on the barrels. Each barrel is marked on both heads (in white oil-colors, the head painted black) with the number of the barrel, the name of the manu- facturer, year of fabrication, and the kind of powder, — cannon, (used for heavy cannon,) mortar^ (used for mor- tars and field cannon,) or mnislcet — the mean initial ve- locity, and the pressure per square inch on the pressure- piston. Each time the powder is proved, the initial ve- locity is marked below the former proofs, and the date of the trial opposite it. 18. Analysis. Whatever may be the mode of proof adopted, it is essential, in judging of the qualities of gunpowder, to know the mode of fabrication and the ANALYSIS. 31 proportions and degree of purity of the materials. The latter point may be ascertained by analysis. In the .first place, determine the quantity of water that the powder contains, by subjecting it to a temper- ature of 212", in a stove or in a tube with a current of warm air passing over it, until it no longer loses in weight. The difference in weight, before and after dry- ing, gives the amount of moisture contained -in the powder. To determine the quantity of saltpetre. In a vessel of tinned copper, like a common coffee-pot, dissolve 1,000 grains of powder, well dried before weighing, in 2,000 grains of distilled water, and heat it until it boils; let it stand a moment, and then decant it on a piece of fil- tering-paper, doubled exactly in the middle ; this opera- tion is repeated three times ; at the third time, instead of decanting, pour the whole contents of the vessel on the filter ; drain the filtei', and wash it several times with 2,000 grains of water heated in the vessel, using in all these operations 10,000 grains of water. After passing through the filters, this water contains in solution all the saltpetre, the quantity of which is ascertained by evaporating to dryness. Dry the double filter with the mixture of coal and sulphur, and take the weight of this composition by using the exterior filter to ascertain the weight of that on which the composition remains; this weight serves to verify that of the saltpetre and to estimate the loss in the process. To determine the quantity of charcoal directly. To separate the sulphur from the charcoal, subject the powder, either directly or after the saltpetre has been dissolved out, to the action of a boiling solution of the 32 GUNPOWDEK. — ^INSPECTIOJS", ETC. sulphide of potassium or sodium, wliicli dissolves tte sulphur and leaves the charcoal, the weight of which may be easily determined. It is important that the sulphides of potassium and sodium used in dissolving the sulphur, should contain no free potassa or soda; for each of these alkalies would dissolve a part of the carbon — particularly of the brown, coal. The sulphide of carbon also dissolves the sulphur contained in powder, and may be used to determine the weight of charcoal which it contains. The charcoal, separated from the saltpetre and sul- phur, is dried with care and weighed, and should then be submitted to analysis in an apparatus used for burn- ing organic matters. The composition of the charcoal may be judged of by comparing it with the results ob- tained in the analysis of charcoal of known quality used in the manufacture of powder. To determine the quantity of sidplmr directly. Mix aiid beat in a mortar 10 grains of dry powder, 10 of carbonate of potassa, 10 of saltpetre, and 40 of chloride of sodium ; put this mixture in a vessel (cap- sule) of platinum or glass, on live coals, and, when the combination of the materials is completed and the mass is white, dissolve it in distilled water, and saturate the solution with nitric acid ; decompose the sulphate which has been formed, by adding a solution of chloride of barium, in which the exact proportions of the water and the chloride are known. According to the atomic proportions, the quantity of sulphur Avill be to that of the chloride of barium used as 16. to 104. 19. Hygrometric qualities. The susceptibility of pow- EESTOEATIOH". 33 der to absorb moisture is due to the charcoal and the presence of deliquescent salts, principally chloride of sodium or common salt. The absorbent power may be judged of by exposing 1 lb. to the air in a moist place (such as a cellar which is not too damp) on a glazed earthen dish, for 15 or 20 days, stirring it sometimes so as to expose the surface better; the powder should be previously well dried, at the heat of about 140°. Well- glazed powder, made of pure material, treated in this way, will not increase in weight more than 5 parts in 1,000, or a half of one per cent. 20. Quickness of burning. The relative quickness of two different powders may be determined by bm"n- ing a train laid in a circular or other groove which re- turns -into itself, one half of the groove being filled with each kind of powder, and fire communicated at one of the points of meeting of the twc^ trains; the relative quickness is readily deduced from observation of the' point at which the flames meet. 21. Restoring unserviceable powder. "When the quantity of water does not exceed 7 per cent., the pow- der may be restored by drying ; this may be effected in the magazine, if it be dry, by means of ventilation, or by the use of the chloride of calcium for twenty or thirty days. Quick-lime may be used ; but the use of it is attend- ed with danger; on account of the heat evolved in slaking. When powder has absorbed from 7 to 12 per cent, of water, it may still be restored by drying in the sun or drying-house; but it remains porous and friable, and unfit for transportation : in this case it is better to work 3 34 GUNPOWDEE. PBESEEVATION. it over. In service, it may be worked by means of tlie rolling-barrels, as described for making round powder. When powder has been damaged with salt water, or become mixed with dirt or gravel, or other foreign substances which cannot be separated by sifting, or when it has been under water, or otherwise too much injured to be reworked, it must be melted down to ob- tain the saltpetre by solution, filtration, and evaporation. 22. storage, &c. In the powder-magazines, the bar- rels are generally placed on the sides, three tiers high, or four tiers if necessary ; small skids should be placed on the floor, and between the several tiers of barrel?, in order to steady them ; and chocks should be placed at intervals on the lower skids, to prevent the rolling of the baiTels. The powder should be separated ac- cording to its kind, the place and date of fabrication, and the proof range. Fixed ammunition, especially for cannon, should not be put in the same magazine with powder in barrels, if it can be avoided. Besides being recorded in the magazine book, each parcel of powder should be inscribed on a ticket attach- ed to the pile, showing the entries and the issue. 23. JPre§ervatioii. For the preservation of the pow- der, and of the floors and lining of the magazine, it is of the greatest importance to preserve unobstructed the circulation of the air, under the flooring as well as above. The magazine should be opened and aired in clear, dry weather, when the air outside is colder than that in- side the magazine ; the ventilators must be kept free ; no shrubbery or trees should be allowed to grow so near as to protect the building from the sun. The moisture of a magazine may be absorbed by chloride of calcium, EFFECTS OF GUNPOWDEE. 35 suspended in an open box under the arch, and renewed from time to time ; quick-lime, as before observed, is dangerous. The sentinel or guard at a magazine, when it is open, should have no fire-arms ; and every one who enters the magazine should take off his shoes, or put socks over them; no sword or cane, or any thing Avhich might occasion sparks, should be carried in. 24. TraMsportation. Barrels of powder should not be rolled for transportation ; they should be carried in hand-barrows, or slings made of rope or leather. In moving powder in the magazine, a cloth or carpet should be spread ; all implements used there should be of wood or copper ; and the barrels should never be repaired in the magazine. When it is necessary to roll the powder, for its bet- ter preservation and to prevent its caking, this should be done with a small quantity at a time, on boards in the magazine yard. • In wagons, barrels of powder must be packed in straw, secured in such a manner as not to rub against each other, and the load covered with thick canvas. EFFECTS OF GUNPOWDER.* 25. History, etc. The projectile arms of the ancients, such as bows, ballistas, and catapults, were operated by the same motive j)0wer — that of the spring. Although large masses were thrown from these machines, the velocity imparted was feeble, as the sjDrings rapidly lost their power, from being bent ; and * Vide Piobeist's Gours d' ArtiUerie. 36 GUNPOWDER. ITS EFFECTS. the introduction of gunpowder, a more certain as well as powerful agent, gradually caused tliem to be super- seded. As before stated, the power of this agent is essen- tially- due to the almost instantaneous development of expansive gases and heat by combustion ; and although its properties were known for a long time, its use was at first confined to fireworks and incendiary composi- tions alone. The advantage of using an agent capable of commu- nicating great velocity to a projectile, arises not only fi'om the intensity of the shock, the possibility of dis- abling a large number of men, and penetrating very re- sisting objects, but from the fact that it allows of the use of lighter machines, whereby the projectile can be directed with greater ease and certainty against its object. Although the combustible nature of powder was known in Asia from the earliest times, and its prop- erties were described by Marcus Grsecus and Roger Bacon, its application to projectiles seems to have been a subsequent result of accident. It is stated that about the year 1330, Berthold Schwartz, a monk of Fribourg, was engaged in making experiments Avith a mixture of saltpetre, sulphur, and charcoal, such as described by Marcus Graecus, and had left the mixture in a mortar, covered with a large stone, when it unexpectedly caught fire and exploded, throw- ing the stone to a distance with great force. The ex- perim-ent was repeated, and with such success that mili- tary men saw at once that it could be applied to move large projectiles. Its progress as a projectile power, DISCOVERT. however, was comparatively slow, and it was only at the beginning of the 16th century that it was generally ased for military purposes. For a long time after its introduction, gunpowder was used in the form of dust, or " mealed powder/' from which it derived its name ; but it was found diffi- cult to load small arms with gunpowder in this condi- tion, on account of the moisture which sometimes collects in the bore after a few discharges. To overcome this difficulty, it was given a granular form, and received the name of " musket powder." It was soon discovered, however, that two parts of grained powder produced as much effect as three parts of mealed powder ; but the larger fire-arms of the day had not sufficient strength to resist this increased force, and mealed powder continued to be used until the close of the 16th century. At first, the ingredients of powder were converted into cake with a hand-pestle; a process which gave grains of very irregular size and shape. It was after- ward discovered that the quality could be much im- proved by careful manipulation, without sensibly alter- ing the proportions of the ingredients first established. Any improvement in gunpowder which increases its strength, also increases its injurious effects on the arms in which it is used. It becomes necessary, therefore, to study the form and thickness of fire-arms, and the na- ture of the agent whose operations they are intended to restrain and direct. It is impossible to embrace in a single glance the de- tails of a phenomenon as complicated as the explosion of a charge of powder. The senses cannot detect the relations which exist between the partial operations of 38 GUNPOWDER. TIS EFrECTS. a phenomenon, where they are produced with such ra- pidity that they seem blended into one. In this case the only sure method of investigation is to separately study the different facts, and then unite them as a whole, borrowing from the physical sciences a thorough knowl- edge of the substances operated upon. If the numerous circumstances which influence the results of the explosion of gunpowder, and the enor- mous expansive force which is developed in its limited duration, prevent us from accurately determining the measure of its effects, we can at least determine the limits between which this measure is included ; which is sufficient for artillery purposes. Prom the results thus obtained were calculated the iron and bronze how- itzers introduced to supersede those of Gribeauval's sys- tem. With less- thickness of metal, these pieces were found to answer every requirement of service; a fact which tends to confirm the accuracy of the data from which they were constructed. 26. Explosion. The phenomenon of the explosion of powder may be divided into three distinct parts, viz. : ignition, inflammation, and combustion. By ignition is understood the setting on fire of a particular point of the charge; by inflammation, the spread of the ignitisn from one grain to another ; and by combustion, the burning of each grain from its sur- face to centre. 27. ignition. Gunpowder may be ignited by the electric spark, by contact with an ignited body, or by a sudden heat of 572° Fahrenheit. A gradual heat de- composes powder without explosion by subliming the sulphur. Flame will not ignite gunpowder unless it COMBUSTIOK. 39 remains long enough in contact with the grains to heat them to redness. Thus, the blaze from burning paper may be touched to grains of powder without igniting them, owing to the slight density of the flame, and the cooling effect of the grains. It may be ignited by fric- tion, or a shock between two solid bodies, even when these are not very hard. Experiments in France, in 1825, show that powder may be ignited by the shock of copper against copper, copper against iron, lead against lead, and even lead against wood ; in handling gunpowder, therefore, violent shocks between all solid bodies should be avoided. The time necessary for the ignition of powder varies according to circumstances. For instance, damp pow- der requires a longer time for ignition than powder per- fectly dry, owing to the loss of heat consequent on the evaporation of the water ; a powder, the grain of which has an angular shape and rough surface, will be more easily ignited than one of rounded shape and smooth surface ; a light powder, more easily than a dense one ; and a powder made of a black charcoal, more easily than one made of red, inasmuch as the latter is compelled to give up its volatile ingredients before it is acted on by the nitre. 28. Connbustioii. The velocity of combustion is the space passed over by the surface of combustion in a second of time, measured in a direction perpendicular to this surface. The diameter of the largest-size grain of mortar- powder does not exceed 0.1 inch ; the time of its com- bustion, therefore, is altogether too transient to be ascertained by direct observation. It may be deter- 40 GUIifPOWDER. ITS EFFECTS. mined by compressing the composition into a tube and burning it, or by burn- ing tbe " press-cake." In the latter case, take a prism of the cake about fourteen inches long and one inch square at the base. Smear the sides with hogs' lard, and place it on end in a shallow dish of ^^ water. The object of the lard is to pre- vent the spread of the flame to the sides ; and the water is to prevent the lower end from being ignited by burning drops of powder. Set the upper end on fire, and note the time of burning of the column with a stop-watch beating tenths of seconds. In either way it will be shown that the composition, if homogeneous, burns in parallel layers, and that the velocity of combustion is uninfluenced by the size of the column, or by the temperature and pressure of the surrounding gas. The velocity of combustion of dry French war- powder is thus found to be 0.48 in., and of English powder, which American powder closely resembles, it is about 0.4 in. It may be shown by direct experiment that the burning of a grain of powder in a fire-arm, is progres- sive, and that the size of the grain exerts a great influ- ence on the velocity of the projectile, especially in short arms. For this purpose take a mortar eprouvette and load it with a single fragment of powder weighing forty-six grains ; fire it, and the ball will not be thrown out of the bore ; divide the same weight into seven or eight fragments, and it will barely be thrown out of the COMBXrSTIOJT. 41 bore ; divide it into fifteen fragments, and it will be ttrown about ten feet; fifty fragments will tlirow it about tMrty feet ; and the same weight of cannon-pow- der, about one hundred and seventy feet. The progressive burning of powder is further con- firmed by the fact, that burning grains are sometimes projected from a gun with sufficient force to perforate screens of paper, wood, and lead, at considerable dis- tances. It is even found that they are set on fire in the gun, and afterward extinguished in the air before they are completely consumed. The large grains of powder used in the fifteen-inch columbiad are thrown out burn- ing, to a distance of one hundred yards. The velocity of combustion of powder varies with the nature^ proportions^ trituration^ density ^ and condi- tion of the ingredients. Purity of ingredients. To secure the greatest ve- locity of combustion, it is necessary that the nitre and sulphur should be pure, or nearly so. This can always be effected by a proper attention to the prescribed modes of refining ; but with the charcoal it is different, for the part which it plays in combustion depends upon certain characters which are indicated by its color and texture. The velocity of combustion will be greater for red charcoals than those that are black and strongly calcined ; and for light and friable charcoals, than those that are hard and compact. It appears, in fact, to be nearly proportioned to the combustibility of the char- coals given in the tables on page 19. Proportions. The proportions of the ingredients have a very great effect on the combustion ; by vary- ing them, all velocities between and .55 inch can be ,42 GUNPOWDEE. ITS EFFECTS. obtained ; tlie latter number can scarcely be exceeded. The proportions whicli give a maximum, appear to be comprised between the two following: Nitre, 76. Charcoal, 15. Sulphur, 9. " 76. " 14. " 10. As it is often useful in preparing fireworks to know the proportions which will give a certain velocity of combustion, a table is given of a series of proportions of nitre, sulphur, and charcoal, and the corresponding velocities of combustion : Sixty parts of nitre, compounded with certain pro- portions of sulphur and charcoal, gave the following velocities : Parts of Sulphur. Parts of Black Charcoal. 5 10 11 15 20 30 60 Inch. Inch. Inch. Inch. Inch. Inch. Inch. Inch. .0 . 02 . 11 .14 .24 .34 .43 .07 5 .0 .05 .24 .30 .43 .47 . 35 .00 8 .0 .06 .50 .51 .49 .41 .20 .00 10 15 .0 .08 .47 .49 .47 .39 . 16 .00 . . 11 .43 .44 .36 .35 . 14 .00 20 .0 .16 .39 .40 .38 . 30 . 10 .00 30 60 .0 .2Y .34 . 33 .29 .21 .01 .00 .0 .00 . 00 .00 .00 . 00 .00 .00 It will be seen that the proportions 6 — 1 — 1 are among those that give the greatest amount of gas in a given time, other circumstances being equal; for the TRirtTEATION. 43 reason, that the weiglit burned during this time is greater, and because each unit of weight gives a greater volume of gas. Trituration. Trituration of the ingredients increases the velocity of combustion ; and this increase is much greater as the proportions approach those which give the greatest velocity. For the results of experiments on this point, see accompanying table : i Velocity of combustton. Bemarks. Composifcion. A. B. c. Ho lire. Inches, Inches. Inches. 1 2 3 4 5 10 .12 .31 .38 .40 .44 .46 .48 .13 .25 .29 .32 .34 .35 .37 .0189 .0192 .0200 .0204 .0212 .0216 .0236 Compositions dry. Nitre. Ch'cnnl, Sulphnr. Composition. A, 75.00 12.5 12.50 Gunpowder. B, 68.00 12.0 28.00 Fuze composition. C, 66.66 2.0 31.34 Port-fire " The nitre was taken as it came from the refinery. The sulphur and charcoal had already been triturated in the roll- ing-baiTels. Density. For each set of proportions, the maximum velocity corresponds to a very small density. By in- creasing the density, the velocity is diminished; and more rapidly for quick compositions than slow ones. When in the form of a dust, gunpowder composition burns more slowly without compression than with it. For the results of experiments on the preceding compo- sitions, see the following table ; the trituration was ex- tended to ten hours : 44 GUNPOWDEE.— ITS EFFECTS. Density. Velocity of combustion. Kemarks. t Composition. A. B. C. 0.80 .360 .310 1 The pulverized composition is sirn'ily poured into a tnbe, and settled bv 1.00 .440 .410 .0319 striking lightly on a table. The composition poured in as above, and compressed under a weight of 22 lbs. without shock. 1.20 .470 .390 .0295 Composition driven with a mallet weighing 2.2 lbs., falling through a height of 3.9 inches. 1.40 .480 .380 .0252 Same, save the height, which was 27 inches. 1.60 .890 .366 .0224 These densities were obtained by in- l.SO .443 .360 .0220 creasing the number of blows with the ma let for each ladleful of compo- sition. 2.00 .340 The density of a composition under the 2.16 .330 same pressure, increases with the trituration of the ingredients. Moisture. By moistening the composition witli pm-e water, alcohol, or vinegar, and then drying it com- pletely;^ the velocity of combustion is increased. "With pure water alone, this increase of velocity may amount to 0.1 of an inch. On the contrary, the velocity is diminished where oils, fatty or resinous substances, are added to the composition, or when it incloses water or other liquids. Vivy Powder, or one containing ^ per cent of moleture, lias a velocity of 0.4S in. H " " " 0.39 in. 2i « " " 0.83 in. 29. Ijslw of formation of gaseous products. When the form and size of the grains and the velocity of com- bustion are known, we can ascertain, at any given mo- rOEMATION OF GASEOUS PE0DTJCT8. 45 Fig. 2. ment, the amount of powder consumed, as the velocity is uniform and independent of the surface. Spherical grain. Take a spherical grain of powder of homogeneous structure, one that will completely burn up in yV of a second. Apply fire at any point of its surface, the flame will immediately envelop it, and burn away the first spheri- cal layer ; if, for example, we suppose the time of this partial combustion be -^ of the time required to burn up the entire grain, then the radius of the remaining sphere will be only -^-^ of the first ; but the volumes of spheres being to each other as the cubes of their radii, the primitive sphere will be to the one which remains after the burnino- of the first layer, as 1.0 is to 0.729, the cube of .9. Subtracting the second of these numbers from the first, we shall have 0.2 '71, which expresses the difference of volumes of the two spheres, or the amount consumed in the first yV of time, compared to that of the entire grain. By making similar calculations on the other layers, we shall obtain the results contained in the following table : Time of burning 0.000 .100 .200 .800 .400 .500 .600 .701 .800 .900 1.000 Decreasing radii 1.000 .900 .SOD .700 .600 .500 .400 .800 .200 .100 0.000 1.000 0.000 .T29 .271 .512 .488 .848 .657 .216 .784 .125 .875 .064 .986 .027 .97a .008 .992 .001 .999 0.005 1.000 Volnmes burnt Voluines burnt in eacli 0". 01 0.000 .271 .217 .171 .127 .091 .061 .087 .019 .007 0.001 It will be seen from this, that for equal intervals of time, those taken in the first period of combustion give forth very much larger amounts of gas than those taken in the last. If, instead of a sphere, we suppose the 46 GUNPOWDER. ITS EFFECTS. grain to be ?k polyliedron circumscribing a sphere, the burning layers being parallel, the decreasing grain will continue to be a similar polyhedron, circumscribing a sphere. The results given in the table will be strictly true for this case, as well as for grains of conical or cylindrical form, provided their bases be equal to their heights. General formula. A general formula may be de- duced to show the amount of gas developed at any instant of the combustion of a grain or charge of pow- der. For this purpose take a spherical grain of powder, and consider it inflamed over its entire surface. Let t represent the time of burning, from the in- stant of ignition to the moment under consideration: t\ the time necessary to burn from the surface to the cen- tre, or total combustion: -ff, the radius of the grain. Since the combustion passes over the radius R in the time V, the velocity of combustion is equal ~p-i ^'^^ r> . for the time t, it will pass over the space t — or R— • t' t' the radius of the decreasing sphere will therefore be all — —) The volume of the grain of powder and that of the decreasing sphere are —nR^ and 4 77 3 R^il — ^X respectively; and their difference, or the quantity of powder burned, will be equal to r-(-(-7)) GENERAL' EOllMULA. 47 The first factor of this expression represents the primitive volume of a grain of powder, and the other expresses the relation of the volume burned to the primitive volume. The same expression will answer for all the grains of a charge of powder, if they are of the same size and composition ; consequently, if Ave let A represent the volume or weight of the grains composing a charge of powder, the quantity remaining unbumed after the time t will be represented by ^| 1 -); and the quantity burned,by.4(l-(^l-^J| Although the grains of powder are not spherical, their sharp angles are paitially worn away by rubbing against each other in glazing and in transportation ; and the mode of fabrication and inspection reduces the variation in size vfithin narrow limits ; therefore, if we examine the influence which the actual form and size of the grains exercises over the phenomenon of combustion of powder, we shall find that the effect varies but slightly from that due to the spherical form. Application to ordinary powder. Take a grain of ob- long form, like that of a spheroid, or cylinder termi- nated by two hemispheres: it will present a greater surface than a spherical grain of the same weight, and consequently the amount of gas formed from it in the first instants of time, will be greater, and the dui'ation of the combustion will be less. It can be shown, how- ever, that so long as the size of the grains is kept with- in the regulation limits, this influence will be slight. To do this, take an oblong grain the cylindrical part of 48 GUNPOWDER. ITS EFFECTS. wMcli has a diameter of .054 in., let it be terminated by two hemispheres, and have a total length of .097 in. (these being the minimum and maximum size of a grain of French cannon-powder, respectively) ; its weight Avill be about .07 grain, or -^{-^ of a gramme^ and with a velocity of combustion of 0.48 it will take 0.056" to burn up completely. French war-powder is composed of grains of different weights, numbering about 310 to ev&j gra^nme, or 15.4 grs. Troy. If, therefore, powder contain oblong grains of the size stated above, there must be others still smaller : if we suppose them to be in equal quantities, and the larger to be ■j\-^ of the unit of weight, then the smaller must be equal to -^\-^ of the unit of weight ; which would be equal to spheres Avith a radius of 0.028 inch. Comparing the quantities of gas developed in intervals of .008", or about \ of the time necessary for the combustion of the smallest grains, we obtain the result in the following table : — • Kinds of grains of Powder. Relation of the volume of powder burned, to the vol- ume of the grains after a time of 0".008 0".016 0".024 0".0S2 0".040 0".048 0".05G Elongated grains, diamr. .054 in. ; length, 0.098 in.,— 210 to the gramme, or 15.4 grs., Spherical grains ol 410 to the gramme, or .056 in. diameter, Elongated and spherical grains as above, in equal quantities, form- ing a mixture of 310 to the gramme, Spherical grains of 310 to the gramme, or 0.0G3 in. diameter, DiSerenee between mixed grains and spherical grains of the same mean weight, 0.310 0.351 0.333 0.330 0.003 0.555 0.G16 0.585 0.580 0.005 0.V31 0.194 0.166 0.158 0,008 0.8G4 0.901 0.S85 0.815 0.010 0.946 0.968 0.958 0.948 0.010 0.981 0.994 0.900 0.985 0.005 1.000 0.999 0.999 0.998 0.001 The differences in the results do not much exceed -J— INFLAMMATION. 49 and may be neglected in practice ; we may accordingly consider all tlie grains of a charge of powder as spheres with radii corresponding to their mean weight. This mean weight is an important element, and may he de- termined ly counting the number of grains in a given cJiarge, and dividing the weight of the charge ly this number. In war-powder the largest portion of each grain is burned in the first two-tenths of the time required to consume the entire grain : as it has been shown that a grain of ordinary cannon-powder requires 0.1 second for its combustion, the largest portion of the grain will be burned in the first -^^-^ of a second. If we consider the velocity of the projectile on leaving a gun, and th^ time necessary to overcome its inertia in the first period of its movement, we shall see that a very large portion of each grain is burned up before the projectile leaves the gun. If the size of the grain he increased, the effect will he to diminish the amount of gas evolved in the first instants of time, and to diminish the pressure on the hreech* This principle has been made use of lately to increase the endurance of large cannon. 29. iiiflammatioM. When grains of powder are uni- ted to form a charge, and fire is communicated to one' of them, the heated and expansive gases evolved, insin- uate themselves into the interstices of the charge, en- velop the grains and ignite them, one after the other. * Tliis idea has been carried out more fully in the experiments of Captain Rodman, by converting the powder into one or more cakes, which are perforated with numer- ous small holes for the passage of the flame. In this way a large portion of the powder is consumed on an increasing instead of a decreasing surface, and the amount of gas given out in the last moments will be greater than in the first; and thus the strain on the breech. -of a gun may be very much diminished without pro- portionately diminishing the velocity communicated to the projectile. For actual results obtained with this kind of powder, see Note appended to section 103. 4 50 GTJNPOWDEE. ITS EFFECTS. This propagation of ignition is called inflamTnation, and its velocity the velocity of inflammation. It is much greater than that of combustion, and it should not be confounded with it. The velocity with which inflamed gases move in a resisting tube, like a cannon, is very great. Hutton cal- culated it to be from 3,000 to 5,000 feet per second ; and Eobins determined it by experiment to be about 7,000 feet per second. But when these gases are forced to pass through the interstices of powder, the resistance offered will consider- ably diminish the velocity of their expansion : it is found to vary with the form and size of the grains ; and may be supposed to be reduced to 33 feet per second. The velocity of combustion, as before stated, is only .48 inch 2oer second. Although the velocity of inflammation of a train of powder can afford but an imperfect idea of this velocity in a gun, it may be interesting to study it. The velocity of inflammation of a train of powder generally varies with the size of the grains, with the quantity of powder employed, and the disposition of the surrounding bodies, as A^dll be shown by the following results of actual experiment. The amount of powder in each train was about .11 lb. to the linear foot, and the time corresponding to the distances was one second. On a plane surface in the open air, . 7.87 feet. In an uncovered trough, . . . 8.13 " In a linen tube, .... 11.38 " In the same- tube placed in the trough, 17.48 " In the trough covered up, . 27.88 " INFLAMMATION. 51 These velocities are less than those obtained in fire- arms, for the reason that the powder is not only confined at the sides, but at one end, which was not the case in the experiment with the covered trough, where it could expand in both directions. A velocity of more than three hundred feet can be obtained by burning quick-match inclosed in a cloth tube. The size of the cross-section influences the velocity, as was shown by burning a train containing .062 lb. per foot in an oiDcn trough : the velocity was S.YY feet, in- stead of 7.87 feet; and in a covered trough it was twenty feet, instead of 27.88. The velocity, therefore, increases with the cross-section of the train. To determine the influence of the size of the grains on the velocity of inflammation, two trains were fired, one composed of fine grains, and the other of large ones ; the velocity of the first was 8.2 feet, and the second was 7.54. This difference was due to the greater amount of gas developed by the small grains in the first instants of combustion. The nature of the charcoal exerts an influence, the black being more favorable to inflammation than the red. For a specific gravity of 1.3, the velocity is 7.5 feet. li u "16 " "72 " " " " 1.8, " " 6.2 " Light powder is therefore found to be more inflam- mable than heavy. If the grains be round the interstices are larger, and more favorable to the passage of the flame, and the in- 52 GUNPOWDEE. PEODTJCTS OF COMBUSTIOIf. flammation of the mass. If they be sharp and angu- lar, they; will close upon each other in such a way as to reduce the interstices; and although the ignition of such grains may be more rapid, its propagation will be diminished. It has been shown that, when powder is burned in an open train, fine powder inflames more rapidly than coarse ; such, however, is not the case in fire-arms, owing to the diminution of the interstices. If a charge were composed of mealed powder, the flame could no longer find its way through interstices, and the velocity of in- fliimmation and combustion would become the same. The velocity of inflammation of powder compressed by pounding is about .64 inch, while that of mealed pow- der in the same condition is only .45 in. PEODUCTS, ETC., OF COMBUSTION 30. WatMre o4 products. Temperature and atmos- pheric pressure considerably influence the products ob- tained from burning gunpowder. When exposed in the open air to a temperature gradually increasing to 572° Fahrenheit, the sulphur sublimes, taking with it a j)or- NoTE. — By compressing grain-powder under a hydrostatio press it may bo con- verted into a solid cake, and be used in loading flre-arms, in place of the ordinary cartridge. No cement is required to unite the grains, as the pressure brings the particles of the surface of the grains within the limits of cohesive attraction, in tho same way that artificial limestone is formed by compressing sand. As the pressure diminishes the interstices of the grains, it also diminishes the velocity of inflammation, and the rapidity with which the charge is converted into flame. Experiments made at "West Point, on some specimens of powder thus prepared by Dr. Doremus, of New York, showed that the pressure on the surface of the bore may be increased or diminished by diminishing or increasing the pressure on the cakes. The cakes were covered by a water-proof, but highly inflammable varnish, wiiich protected the powder from moisture, without apparently diminishing its inflammability. NATUEE OF PRODUCTS. 53 tion of the carbon. This was shown by Saluces, who passed the volatilized products through a screen of very fine cloth, and found carbon deposited on it. Powder may be, therefore, completely decomposed by a gradual heat, without explosion; but when suddenly brought in contact with an ignited body, the temperature of which is at least 5Y2° Fahrenheit, the sulphur has not time to sublime before explosion takes place The proportions for war-powder for the United States service are seventy-six parts of nitre, ten of sulphur, and fourteen of carbon. By the atomic theory the proportions should be 74.64 nitre, 11.85 sulphur, 13.51 carbon. If we adopt these last proportions, the formula for gunpowder becomes {NO'+KO)+S+?,0. If we suppose the ingredients to be pure, and to arrange themselves under the influence of heat according to their strongest affinities, there will result one equivalent of nitrogen, three of carbonic acid, and one of sulphide of potassium, for {NO^+KO) +8+ 3 0^N+ 3 CO'-^SK. The products are, therefore, solid and gaseous. Usually, powder contains a slight quantity of moisture ; the in- gredients are not absolutely pure, nor are they propor- tioned strictly according to their combining equivalents ; it might be expected, therefore, that the actual would differ from the theoretical results. The actual gaseous products obtained by combustion are, principally nitrogen and carbonic acid, sometimes carbonic oxide, a little euVphwretted hydrogen, carburetted hydrogen, and nitrous oxide. The solid products are, sidphide of potassium, sulphate of potassa, carbonaie 54 GUNPOWDER. ^PEODTJCTS OF COMBUSTIOlir. of potassa (mingled with, a little carbon)^ and traces of sul/phuT, When the sulphide of potassium comes in contact with the air, it is converted into sulphate of jDotassa, and gives rise to the white smoke which follows the ex- plosion of gunpowder. A portion of the sulj)hide is sometimes condensed on the surface of the projectile, which accounts for the red appearance of shells, some- times observed in mortar-firing. The solid products are probably volatilized at the moment of explosion by the high temperature which accompanies the combustion; but, coming in contact with bodies of much lower temperature, they are imme- diately condensed. In chamberfed arms, small drops of sulphur- may be observed condensed on the sides of the bore, which shoAV that the sulphur has been volatilized ; and we know that good powder burns on paper and leaves no trace. This fact, however, was most com- pletely shown by the experiments of Count Eumford. This celebrated observer used a small eprouvette of great strength, which he partially filled with powder, and hermetically closed with a heavy weight. The powder was fired by heating a portion of the eprouvette to redness. Whenever the force was sufiicient to raise the weight, the entire products escaped; when it was not, a solid substance was found condensed on the sur- face of the bore furthest from the source of heat. 31. Temperature. The temperature of the gaseous products of fired gunpowder has been variously estima- ted. Saluces determined by experiment that pure cop- per, which melts at a temperature of 4,622 Fahr., was not always melted by them ; while brass, the melting- BETEEMINATION OF FOECE. 55 point of wMcli is albout 3,900 Fahr., was invariably melted ; lie was, therefore, induced to place tteir tem- perature at about 4,300 Fahr. As metals absorb a large amount of lieat before melting, it is probable that tlie temperature of fired gunpowder is actually more than is here stated. DETEKMINATION OF THE FORCE OF GUNPOWDEE. 32. Absolute force. The absolute force of gunpow- der is measured by the pressure which it exerts when it exactly fills the space in which it is fired. Various experiments have been made to determine mechanically the absolute expansive force of fired gunpowder, but with widely different results. Robins estimated it at 1,000 atmospheres, Hutton at 1,800, D'Antoni from 1,400 to 1,900, and Rumford carried it as high as 100,000 atmospheres.* These discrepancies arise, in a great measure, from the very great difference which exists be- tween the expansive force of the gases in the different mo- ments of combustion, and from a want of coincidence in the observations. The apparatus used by Rumford to determine this point consisted, essentially, of a small eprouvette, E, capa- ble of holding exactly 25 Pj 5 grains of powder. The orifice * Eodman's experiments show the absolute pressure to be at least 13,333 atmos- pheres, or 200,000 lbs. to the square inch. 56 GUNPOWDEE. FORCE. was closed with a heavy weight, and the powder was fired by heating the stem of the eprouvette, S, with a redhot cannon-hall, B. For the first trial, he filled the eprouvette with 25 grains of the best quality of dry pow- der, and rested upon the cover the knob, C, of a 24-pd. gun, whose weight was 8,081 lbs. Notwithstanding its great strength, the eprouvette was burst at the first fire into two pieces ; and the 24-pdr. was raised. Rumford endeavored to show from the weight thus raised, that the pressure of the gases on the sides of the eprouvette was greater than 10,000 atmospheres. He further attempted to show, that as the tenacity of good iron is equal to 4,231 times the pressure of the atmosphere on the same surface, and as the surface of rupture was 13 times that of the bore, the force necessary to produce the rupture of the eprouvette must have been 13x4,231, or 55,003 atmospheres. There are circumstances attending this experiment which should be taken into account, and which will very materially diminish this result. They are, the diminution of the tenacity of the iron, due to heating the eprouvette to produce explosion, and the incorrect method by which Rumford estimated the strength of a hollow cylinder subjected to a strain of expansion. 33. Relation betw^een (IenL§ity and force. Experi- ments were continued, with a similar apparatus, to de- termine the relation between the density and the expan- sive force of fired gunpowder. The capacity of the eprouvette was nearly 25 grains. It was fired with vari- ous charges from 1 up to 18 grains; and the expansive force of each discharge was determined by the smallest weight necessary to close the orifice against the escape DENSITY AND FORCE. 57 of the gas. With the results of 85 trials a table was formed, from which a curve was constructed which ex- presses the relation between the density and expansive force of fired gunpowder, from 1 to 15 grains. By analogy and calculation, this curve was continued up to a charge of 24 grains ; and for the density correspond- ing to this charge, the pressure was found to be 29,178 atmospheres. This pressure is much greater than that developed in the explosion of projectiles and mines, owing to the low temperature of the surrounding surfaces, and the large amount of heat which they absorb. It is the same with cannon, for the most rapid firing does not raise the temperature of the bore above 210 Fahr., which is much below that of the eprouvette. Besides, the powder does not completely fill the space in rear of the ball ; and, as powder burns progressively, this space is enlarged before the gases are completely developed, and conse- quently their density is diminished. There is also a loss of force by the escape of the gases through the windage and vent. The following equation expresses the relation found to exist between the density and expansive force of charges of gunpowder, from 1 to 15 grains, fired in an eprouvette the capacity of which was 25 grains, or in other words, for charges in which the densities vary from .04 to .6 : in which p represents the pressure in atmospheres, and d the density of the inflamed products. It will be seen from this equation, that the pressure 58 GTXNPOWDEE. FORCE. increases more rapidly than the density, since the expo- nent of the density is greater than unity. The density of the gases is eq%al to the weight of the powder Iwrned divided hy the space occupied iy the gases. By substituting this in the equation, we can determine the pressure exerted at any given instant of the com- bustion. Although this relation is deduced for a particular kind of powder, it may be used for all service-powders and service-charges without serious error, since the actual amount of gaseous products is nearly the same for all, and the densities of the highest service-charges never exceed O.6.* 34. Force of po-wder when inflammation is instanta- neous. If the size, form, and density of the grains of a charge of powder, the velocity of combustion, and the * The accuracy of Eumford's formula hag been lately verified by a series of experiments made by Captain BodiQan. The apparatus used by this officer con- sisted of a very thick cast-iron shell, to which was attached an indenting piston for determining the pressure on the inner surface, or powder cavity of the shell. The following table shows the pressures calculated by the formula and the pres- sures obtained by the experiments, for three different densities : DcnBity. Pressure by Eumford's Formula. Pressure by Rodman's Kxperiments, d=4 1,290 lbs. 2,9Q0 " 3,T00 '■ 1,066 lbs. 2,525 " 3,220 " The lesser pressure obtained by Rodman's experiments may be in a great measure explained by the facts, that the shell was not heated, but fired with a friction tube, and that the gas was allowed to escape through the vent. Further experiments were made which sliow that so long as the volume of the charge bears the same proportion to the space in which it is fired, the pressure on the unit of surface remains the same, no matter what may be the amount of the charge. This follows also from Eumford's formula, since the value of ^ is not affected so long as d remains the same. FOECE. 59 space in .whicli it is contained, are known, we can deter- mine the density of the gaseous products at any partic- ular moment of combustion. For this purpose, take the case in which the inflammation of the whole charge is considered instantaneous, and let P be the weight of the charge, d' the density of the composition of which the powder, is made, F'the space in which the gases expand, i! the time of combustion of a single grain, t the time since the combustion began, d the density of the gases at a given instant. According to section 29, the weight of powder remaining after a time, ^, will be equal to P\^ ,) , P/ t\ and the volume will be equal to -?,( 1 ■,); the weight of gaseous products evolved will be equal to Pi\ — {\ ;j j; and their density will be equal to this quantity divided by the space T^ diminished by the space occupied by the powder unburnt at the end of the time t. Or, P d= H-jH d\ t'J V-^. Let IiT represent the ratio of the weight of powder which would fill the space V, to the weight of the charge P, and P the gravimetric density, or weight 60 GUNPOWDEE.— rOKCE. of a unit of volume of powder, we shall have .the equa- tion, and the formula for the density of the gaseous products becomes, If the charge fill the entire space F, JT^l, and -9 (1) d=i)- D "When the grains are consumed, ^=: V, and d^= — ; and if ^r=l, d^D. Having determined the mean density of the gaseous products at any instant of the combustion, we can de- termine the pressure exerted on the enclosing surfaces by means of Rumford's formula P= 1.841 (905t?)i>"'-'''^'^. This value of P supposes that the entire charge is inflamed at the same time — ^a supposition that is not strictly correct, except for small and lightly-rammed charges. When the charge is large, and well-rammed, as in cannon, it is necessary to take into consideration the time of inflammation. 85. Density Avhen the inflammation i§ not instan- taneous. In a majority of cases the preceding formulas will give the relation between the density and expau- FORCE. 61 sive force of gunpowder, without sensible error; but when the grains are small, and the charge is com- pressed by ramming, the interstices are diminished in size, and the inflammation is comparatively less rapid ; besides, the size and form of the charge exert an in- fluence which increases with its length. It is- proposed, therefore, to modify the formulas, and adapt them to the most general case, by considering the inflammation progressive. Take a charge of powder, of any form whatever, and consider it ignited at the point A, the inflammation will reach the surface of the concentric zone J^, the radius of which is tv, in the time t, v being the velocity of inflammation. There will be portions of the charge situated within this zone which the flame will not have reached ; others in which the combustion is completed ; and others, between these two, in which the inflammation is completed, but the combustion is only partially completed. See figure Y. Kg. 6. Kg. T. The extent of the inflamed zones being determined by the form and dimensions of the charge, exerts a great influence on the development of the gases, and conse- quently on their density. If the velocities of inflammation and combustion be known, the quantity of gas formed from each zone can be calculated, and the question becomes one of analysis. 62 GUNPOWDEK. FOECE. In this calculation, tte integral limits wliicli refer to tlie extent of the zones are determined b}^ the surface of the charge ; and those which refer to the progress of the combustion of the grains will be the point of ignition and the surface of inflammation ; or, if d be the time ne- cessary for the flame to reach the surface of the zone, the radius of which is as, the time of partial combustion of a grain of this zone will be t—e, and its complete combus- tion is expressed by the relation t=t'-\-d. For this zone the density of the gaseous products at the instant of inflammation will be <^r=:0, and when com- pletely consumed d=D. The intermediate values may be determined by for- mula (1) a— i)l — 4yr by substituting t—d for t, and supposing ,2=1, should the charge completely fill the space in which it is burn- ed. Integrating between the determined limits, we ob- tain the mean density of the gases developed. The solution of this question, in a general sense, is very diflacult, and requires the aid of the differential calculus. There are particular cases, however, where the solution is not difl&cult ; for instance, where the charge is of cylindrical form and is placed at the bottom of the bore of a gun. 36. Calculation oi tlie density of a cliargc of cylin- drical form. Although the charge of a gun is ignited at the rear and upper portion, we may consider that all portions of the circular layer at the bottom are inflamed FORCE. 63 at once, and that tlie inflammation spreads by parallel layers throughout its extent. The space at the bottom of the bore, and the escape of gas through the vent, favor this supposition. Let Zi represent the total length of the charge, and e' the time necessary for' the inflammation to pass over this length. Let us assume that e'=-nt\ t' being the time necessary for the combustion of a single grain of the charge ; n, therefore, is the ratio of these times. The velocity of inflammation will be -7, or —,; and — ; will represent the portion of the charge inflamed in the time t. The length of the charge which will be consumed (and no portion can be entirely consumed unless t>t') will be (t—f) — -,; and the thickness of the nt o burning layer will be the difference between these tw quantities, or — : which is constant. n If the area of a section of the charge, perpendicular to its axis, be taken as the unit of surface, the volumes may be represented by their lengths. Divide the length of the burning portion into a number, h, of smaller sections, the length of one of the smaller sec- tions will be equal to ^ ; if A be very large, the grains n/i of each very small section may be considered in the same stage of combustion, and the radii of the consumed layers in each grain of the small sections wiU be represented in parts of the primitive radius, as fol- lows : — 64 GUKPOWDEE. FOECE. For the 1st, 2d, Sd. . . A-2, A-1, A, sections. h A-1 A-2 _1 A i- 7i' h ' h ' ' ' K V h' The radii of the burning grains will be, 1 2 A— 3. A— 2 7i— 1. ""' I ~K ■ ■ ~r' ~A ' A ' and the corresponding volumes of the un burnt portions will be represented by. The volumes burned will be represented by, If D represent the gravimetric density of the pow- der, the weight of each small section will be -^B. and nh the weight of the gaseous products in all the sections Avill be Z^U lB+2«+3^+4^..+(A-l)« nf \ "' T? but we know in general terms that ^ therefore the sum of the weights of the gases formed will be. If we suppose h, the number of sections, to be infi- nite, the above expression will reduce to LP ZZ> FOECE. 65 The portion of the charge entirely consumed being equal to — —Z, its weight will be ^^LD, and the total weight of gaseous matter developed will be, - nt ^* n nt' \ 4 / The space which they occupy is equal to the volume of the inflamed portion of the charge, diminished by the volume of the unburned grains at the end of the time t; the volume of the burning powder is — , and n its weight is —D. The weight of the portion burned being equal to |- ; that which remains unburned n will be equal to \- , and the density of the grains being d', their volume will be equal to f . The nd' volume into which the gases expand will consequently be equal to nt' ' nd' ' Finally, the mean density of the gases at the instant t, will be, nt \ 4.J _ 4. nt' * nd' W From this it will be seen that the density is indepen- dent of the velocity of inflammation and length of the charge. The formula, however, can only be applied 5 66 GUKPOWDEB. FORCE. jfrom the instant t=.t' to that in whicli t=^e'—t', that is to say, so long as there exists a portion of the charge in which the combustion is ceasing on its posterior surface, and commencing on its anterior surface. Without committing a serious error, we can, how- ever, apply the formula when t=z^t\ because, in taking the sum of the cubes 0^-l^+2^+3''+. . .+ {h—iy from 1 to (Ji—iy it will only be necessary to take it from l-\ to (7i—iy, which makes an error equal to /A \^ l8_|_2''-(-3l . . + (-— 1 1, or J^ of the total sum, as may be seen by replacing h by - in the expression | — :^ ^ > . If the section of the charge, instead of being equal to the section of the bore of the gun, is only -=, the gases being developed fre6ly in a space ^ times greater, the density D will be diminished in an inverse ratio, and we shall have ^S. ''^ AKd' 37. Application to practice. Thus it will be seen that the density,. and consequently the expansive force of fired gunpowder can be determined at each instant of combustion, either in the case in which the inflamma- tion is considered instantaneous, or Avhen considered progressive. The accuracy of the formulas was verified in France some years since, in the course of a series of experiments PRACTICAL EESULTS. 67 to determine tlie influence which the size and density of grains of powder exert upon the initial velocity of a projectile. There were six different sizes of grains tried, viz. : — .26 in., .21 in., .18 in., .15 in., .10 in. (cannon), .05 in. (musket) ; of each size there were six different densi- ties, viz.: — 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and four different modes of manufacture, making 144 varieties of powder in all. The instruments used were the ballistic pendu- lum, the 4-pdr. gun pendulum, the mortar eprouvette, and the infantry musket. The results of calculation and direct experiment show a remarkable agreement, and may be summed up as fol- lows, viz. : — 1. With the 4-pdr. gun the high densities gave greater velocities when combined with the smallest grains, and vice ver^a, the low densities gave greater velocities when combined with the largest grains. The grains which gave the highest velocities possessed me- dium size and density, or a density of 1.5 combined with a diameter of 0.18 in. 2. "With the mortar eprouvette, which fired a smaller charge than the 4-pdr. gun, the fine-grained powder gave almost invariably greater velocities than the coarse. For a grain of .1 in. (or mortar size), the low- est densities gave the- best results, and for a grain of .05 in. (or musket size), the highest densities gave the best results. 3. With the infantry musket, and a still smaller charge, the superiority of fine grains was more marked for all densities, and particularly so for the least. It would appear fi'om the foregoing, that the size and 68 GUNPOWDEE. — GUN-COTTON. density of grains of powder should be increased in a cer- tain ratio with the weight of the projectile to be moved, the size of the charge,^nd the length and diameter of the bore in which the powder is burned ; and it is for this reason that five different powders have been adopt ed for the military service of this country (see page 27). GUN-COTTON. 38. Gun-cotton, or pyroxiie. The action of nitric acid on such vegetable substances as saw-dust, linen, paper, and cotton, is to render them very combustible. In their natural state these substances are almost entirely composed of lignine, the constituents of which are oxy- gen, hydrogen, and carbon • nitric acid furnishes nitro- gen, a substance Avhich enters into the composition of nearly all explosive bodies. Oun-Gotton was discovered by Prof Schonbein, and published to the world in 1846. His method of pre- paring it consists in mixing three parts of sulphuric acid, sp. grav. 1.85, with one part of nitric acid, sp. gr. 1.45 to 1.50; and when the mixture cools down to be- tween 50° and 60° Fahr., clean rough cotton, in an open state, is immersed in it ; when soaked, the excess of acid is poured off, and the cotton pressed tightly to remove as much as possible of what remains. The cotton is then covered over and left for half an hour, when it is again pressed, and thoroughly washed in running water to remove all free acid. After being partially dried by pressure, it is washed in an alkaline solution made by dissolving one ounce of the carbonate of potash in a gallon of water. The free acid being thus expelled, it GUN-COTTOX. G9 i^ placed in a press, the excess of alkaline solution ex- pelled, and the cotton left nearly dry. It is then washed in a solution of pure nitrate of potash, one ounce to the gallon, and being again pressed, is dried at a temperature of from 150° to lYO". The sulphuric acid has no direct action on lignine, its use in the preparation of pyroxile being to retain the water abstracted from the cotton, and prevent the solu- tion of the compound, which would take place, to a greater or less extent, in nitric acid alone. Cotton, in its conversion into an explosive substance, increases very considerably in weight, owing to the for- mation of a new and distinct chemical compound. Gun-cotton, when properly prepared, explodes at a temperature of about 380° Fahr. It will not, therefore, ignite gunpowder, when loosely poured over it. Under ordinary circumstances, the electric spark will not explode it ; but if the fluid be retarded in its prog- ress by being passed over the surface of a string mois- tened with common water, and in contact with the cot- ton, explosion will follow. From the experiments of Major Mordecai, made at Washington arsenal, in 1846, the following facts regard- ing the use of this substance in the military service, were ascertained: — 1. The projectile force, when used with moderate charges in musket or cannon, is equal to that of about twice its weight of the best gunpowder. 2. When compressed by hard ramming (as in filling a faze), it burns slowly. , 3. By the absorption of moisture, its force is rapidly diminished, but it is restored by drying. 70 GUNPOWDER. GTJW-COTTOW". 4. Its explosive force, or bursting effect, is in a liigli degree greater than that of gunpowder. In this respect the nature of gun-cotton assimilates much more to that of the fulminates than to gunpowder. It is, conse- quently, well adapted for many purposes in mining. 5. Gun-cotton, well prepared, leaves no perceptible stain when a small quantity is burnt on white paper. 6. It evolves little or no smoke, as the jDrincipal resi- due of its combustion is water and nitrous acid ; the lat- ter is made sensible by its odor, and by its effects on the barrel of a gun, which will soon be corroded by it, if not wiped after firing. 7. In consequence of the quickness and intensity of action of gun-cotton, when ignited, it cannot be used with safety in our present fire-arms. An accident of service, such as that of inserting two charges into a musket before firing (which frequently occurs), would cause the bursting of the barrel ; and it is probable that the same result would be produced by regular service charges, repeated a moderate number of times. Note — The following is said to be the improved method of preparing gun- cotton for the Austrian service : The cotton is immersed in the strongest pre- paration of acid — one part of nitric to three parts of sulphuric - and is permitted to remain in the acid bath for forty-eight hours. It is then washed in a stream of running water for four, six, or eight weeks, so as to remove every trace of free acid, which is not the case with gun-cotton made elsewhere. It is prepared for service by spinning it into a thread, which is wound around a stick to form it into a cartridge of the required size. Thus prepared, the in- flammation, which depends on the compactness of the ma. expense. Cast iron. The introduction of cast iron, for laro\' projectiles, was an important step in the improvement of artillery, as it unites in a greater degree than an}' other material, the essential qualities of hardnesr-, strength, density, and cheai)nes« ; it is exclusively used for this purpose in the United States' service. CLASSIFICATION. 73 Compound. Compound projectiles are sometimes made so as to combine the good and correct the bad qualities of different metals. Thus, at the siege of Cadiz, cast-iron shells filled with lead, forming projec- tiles of great strength and density, were thrown from mortars to a distance of three miles and three quarters. For rifle-cannon, projectiles are made occasionally of cast iron, and covered with a soft coating of lead, or other soft metal, to obviate the serious results that might arise from the- wedging of the flanges' in the grooves of the gun. Such is the construction of Arm- strong's projectile in England, and Sawyer's and others, in this country. In the rifle-cannon lately used by the French anny in Italy, it is stated that the flanges which projected into ' the grooves of the bore were made of tin. Considerable success has also been attained in uniting cast iron and wrought iron, and cast iron and soft metal, in such manner as to attain the strength of one metal, and the softness and expansibility of the other. 41. ciassiflcation. Projectiles may be classified ac- cording to their foi-m, as spherical and oblong. Splierical projectiles. Spherical projectiles are com- monly used in smooth-bored guns, and for this pui-pose possess certain advantages over those of an oblong form : 1. They present a uniform surface to the resist- ance of the air as they turn over in their flight. 2. For a given weight they offer the least extent of surface to the resistance of the air. 3. The centres of figure and inertia coincide. 4. They touch the surface of the bore at only one point; they are therefore less liable to wedge in the bore, and endanger the safety of the piece. 74 PEOJECTILEe. 5. Their rebounds on land and water being certain and regular, they are well suited to rolling and ricochet firing. Oblong projectiles. The great improvements which have been made within the last few years in the accu- racy and range of cannon and small-arms, consist simply in the use of the oblong instead of the spherical form of projectile. The superiority of the oblong form has been long known, and for many years used in the sporting rifles of this country; but serious obstacles have always stood in the way of its general adoption into the mili- tary service!. To attain accuracy of flight and increase of range with an oblong projectile, it is necessary that it should move through the air in the direction of its length. Though experience would seem to show that the only sure method of effecting this, is to give it a rapid rotary motion around its long axis by the grooves of the rifie^ numerous trials have been, and are now being made, to- produce the same effect with smooth-bored arms. Centre of gravity^ &c. One of the simplest plans used for this purpose, is to place the centre of gravity, or inertia, in advance of the centre of figure, or resist- ance. If these points be situated in the -long axis of the projectile, as they should be, the forces of propul- sion and resistance, Avhich act in opposite directions, Avill cause it to coincide Avith the line of flight. This plan was tried on a hollow projectile in the time of Louis XIV., by dividing the cavity into two com- partments by a partition, and filling the front one with l)ullets, and the rear one with powder ; but the flight SOLID PBOJECTILES. 75 of these projectiles was uncertain and irregular, and it was observed that some of them burst in the air, and that others struck the object sidewise. Another plan of this kind, proposed by Thiroux, is to make the projectile very long, with its rear portion of wood, and its point of lead or iron, somewhat after the manner of an arrow ; but it does not appear that that method has ever been submitted to the test of practice. Cham-hall. To arrest the motion of rotation of an oblong projectile, thrown under high angles, and with a moderate velocity, it has been proposed to attach a light body to its posterior portion, by means of a cord or chain, which will offer a resistance to the flight of the projectile, and cause it to move with its point fore- most. Nail-hall. This is a round projectile, and has an iron pin projecting from it to prevent it from turning in the bore of the piece. Grooved halls. Attempts have also been made to give an oblong projectile a motion of rotation around its long axis, by cutting spiral grooves on its base for the action of the charge, or by cutting them on the forward part for the action of the air. These plans have not succeeded in practice, for the reason, perhaps, that the projectile naturally turns over end for end, and the air and charge do not act on the grooves with sufficient promptness, energy, and certainty to prevent it. 42. Solid siiot. Projectiles may be further classified according to their structure and mode of operation, as wlid, liollow and case sliot. Solid projectiles. Solid projectiles are used in guns and small-arms, and produce their effect by impact 76 PROJECTILES. alone. When used in heavy guns they are known as solid sTiot, round shot^ or sliot. They are made of cast iron, and on account of their great strength and density, and the comparatively large charges of powder Avith which they are fired, are used when great range, accu- racy, and penetration are required. They are the only projectiles that can be used with effect against very strong stone Walls, or floating batteries covered with wrought-iron plates. Solid shot for guns are classified according to their weight, which, in the United States' land service, is as follows, viz. : Field service, 6 and 12 pounders. Siege service, 12, 18, and 24 pounders. Sea-coast service, 32 and 42 pounders. Solid shot for columbiads are classified according to the diameter of the bore, as 8 and 10 inch solid shot. 43. Bullets. The object of small-arms is to attain animate objects ; their projectiles are, therefore, -made of lead, and are generally knoAvn as hullets. They are both round and oblong ; but in consequence of the great improvements that have been made of late, in adapting the principle of the' rifle to small-arms, the oblong ball is now very generally used in all military services, the round bullet being chiefly retained for use in case-shot. Hound bullets. Round bullets are denominated by the number contained in a pound ; this method is often used to express the calibre of small-arms; as, for in- stance, the calibre of the old musket was 17 to the pound, and the rifle was 32. In 1856, these two calibres were replaced by one of 24 to the pound, that of the new rifle musket. The number is sometimes prefixed to the word gauge, in which case the rifle-musket would SHELLS. 77 be called a 2i:-gauge gwfi. This mode, however, is prin- cipally used to designate sporting arms. The oblong bullet is denominated by its diameter and weight ; for instance, the new rifle-musket ball has a diameter of 0.58 in., and weighs 540 grains. Oblong bullet. The oblong bullet at present used in the United States' service, is composed of a cylinder surmounted by a conoid — the conoid being formed of the arcs of three circles. The cylinder has three grooves cut in it, in a direction perpendicular to its axis, to hold the grease necessary for lubricating the bore of the piece in loading, and possibly to guide the bullet in its flight, after the manner of the feathers of an arrow. A conical cavity is formed in the bottom, in which the gas of the charge expands, and forces the sides of the bullet into the grooves or rifles of the gun. From these grooves it receives a rotary motion around its long axis, which prevents it from turning over in its flight. 44. siieii§. Under the head of Jiollow shot are includ- ed shells for guns, howitzers, and mortars, and hand and rampart grenades. These projectiles are all made of cast iron; and for guns and field howitzers their cali- jji-es are expressed by the weight of the equivalent solid shot, as 12, 24, and 32 pound shells; and for all other howitzers and mortars, by the diameter of the bore of the piece, as 8 and 10 inch shells. Shells have less strength to resist a shock, they are therefore fired with a smaller charge of powder, than 78 PEOJECTILES. SHELLS. solid shot. Their weight, and consequent mean den- sity, is generally about two-thirds that of a solid shot of the same size. Shells act both by impact and explosion, and are used against animals and such inanimate objects as will not cause them to break on striking. The principal parts of a spherical shell are : 1. The comity — ^the shape of which is similar to and concentric with the exterior. The use of the cavity is to contain a bursting charge of powder, if the object be merely to destroy by explosion; or a bursting charge and incendiary composition, if the object be to destroy by explosion and combustion together. The size of the cavity should be as large as possible, to produce the greatest explosive effect ; but as the shell should have sufficient strength to resist the shock of the dis- charge, and sufficient weight to overcome the resistance of the air, the size of the cavity Avill necessarily be sub- ordinate to these conditions, which fix the thickness of the metal. 2. The fuze-Jiole, which is used in inserting the bursting charge, and to hold the fuze which communi- cates fire to it. As the presence of the fuze-hole dimin- ishes the effect of the bursting charge, the diameter of its orifice should be as small as possible. 3. The ears are two small recesses made near the fuze-holes of all shells larger than a 42-pounder, for the purj)ose of in- serting the " hooks," and lifting the shells up to the bore of the piece in loading. A small hole is sometimes made in the upper hemisphere of shells, for the purpose of charging them after the fuze is driven ; but late im- provements in the construction of the fuze allow it to he dispensed with, so that the powder can now be poured GRE]SrADES. 79 directly througli the faze-plug, and the charging can be deferred until the moment of loading. Fig. 10 represents a mortar-shell, and fig. 11 a shell used in a gun or sea-coast howitzer. The mortar-shell is fired with a lighter charge of powder than the gun- shell, and has therefore less thickness of metal. The fuze-hole of the gun-shell, is reinforced with metal, so that the faze will not be driven in by the force of the discharge. This reinforce serves, in a measure, to compensate for the metal taken out of the fiize-hole, and renders the shell more concentric. a. .Fuze-hole. 6. .Reinforce. c. .Cavity. d. .Sides, or thick- ness of metal, e . . Ears. Kg. 10. Pig. 11. 45. Greiiacics. The hand grenade, as its name indi- cates, is a projectile thrown from the hand, against troops in mass. The particular projectile used for this purpose, in our service, is the 6-pounder spherical case-shot. Rampart Grenade. Eampart grenades are intended to be rolled down the rampart of a work, to protect a breach against the attack of a storming column. Shells of any size will answer for this purpose, and particu- larly those which are unserviceable for ordinary j)ur- poses. Grenades are filled with a bursting charge, and are 80 PEOJECTILES. CASE-SHOT. armed with a short fuze,* which is lighted by a match in the hands of the grenadier immediately before it is thrown. They act by the force of their explosion alone. 46. Case-shot. Case-shot are a collection of small pro- jectiles enclosed in a case or envelope. The envelope is intended to be broken in the piece by the shock of the discharge, or at any point of its flight, by a charge of powder, enclosed within it ; in either case, the contained projectiles continue to move on after the rupture, but scatter out into the form of a sheaf or cone, so as to cover a large surface and attain a great number of ob- jects. These projectiles can only be used with effect against animate objects situated at a short distance from the point of ruptirre. The three principal kinds of case-shot in use are grape, canister, and spherical case-shot, or shrapnel. They are adapted to all guns and howitzers below those of 10-inch calibre, and re- ceive their name from the pieces in which they are used. Grape-shot. A grape-shot is com- posed of nine small cast-iron balls, dis- posed in three layers of three balls each. Formerly the balls Avere held together by a covering of canvas and network of twine; but the present Fig. 12. method is more simple and durable. * Ketchum's hand grenade, which has lately been introduced into the Americ.in service, is a small, oblong percussion shell, which explodes on striking a slightly resisting object. To prevent accidents, the "plunger," or piece of metal which communicates the shock to the percussion cap is not inserted in its place untU the moment before the grenade is thrown. CASE-SHOT. 81 The parts of a stand of grape are, two plates, a, a, see Fig. 12, for tlie top and "bottom layers; two rings, ^,3, for the intermediate layer, and a screw-bolt, c, which passes through the plates and unites the whole. A han- dle is formed by passing a piece of rope-yarn through two holes in the upper plate, and tying the ends into knots to prevent them from pulling out. Grape-shot are used in all except the field and moun- tain services. Canister-shot* A canister-shot for a gun contains 27 small cast-iron balls, arranged in four layers, the top of 6, and the remainder of 7 each. A canister-shot for a howitzer contains 48 small iron balls, in 4 layers of 12 each. For the same calibre, it will be seen that the balls used in canister-shot are smaller than those used in grape-shot. The envelope is a tin cylinder, closed at the bottom by a thick cast-iron plate, and at the top by one of sheet-iron. The plates are kept in place by cutting the edges of the cylinder into strips about 0.5 inch long, and lapping them over the plates. To give more solidity to the mass, and preveint the balls from crowding upon each other when the piece is fired, the interstices are closely packed with sawdust. The handle is made of wire, and attached to the thin plate at the top. Canister-shot are used in the field, mountain, siege, and sea-coast services. * The balls for canister for bronze rifle-guns are made of lead, or enclosed in a case of some soft material, to avoid injury to the surface of the bore. 6 Eig. 13. 82 PEOJECTILES. CASE-SHOT. It is stated that canister-sliot were first used in the defence of Constantinople, about the middle of the 15 th century. Spherical case-shot. Though projectiles similar to spherical case-shot were used in France as early as the time of Louis XIV., the credit of perfecting them is due to Colonel Shrapnel of the British army. They were first successfully used by the English against the French, in the Peninsular war. The envelope in the spherical case-shot, is a thin cast- iron shell, the weight of which, when empty, is about one half that of the equivalent solid shot. To prepare this ' shot, it is first filled with round musket-balls, 17 to the lb., and the interstices are then filled up by pouring in melted sulphur or resin ; the object of which Kg. 14. is to solidify the mass of bullets, and prevent them from striking, by their inertia, against the sides of the case and cracking it, when the piece is fired. A hole is bored through the mass of sulphur and bullets, to receive the bursting charge; and, in order not to displace too many bullets, and not to scatter them too far when the shot bursts, the bursting, charge should only be sufficient to produce rupture. If the iron, of which the case is made, were always of suitable quality, and the cavity filled with bullets snugly packed in, there would be no necessity for sul- phur to prevent accidents. In this case, it would not be necessary to remove any of the bullets, as the burst- ing charge would be disseminated through the inter- stices ; and the difficulty, which now sometimes arises BAE-SHOT. 83 from their adhering to fragments of the case, would be entirely obviated. To increase the effect of a small bursting charge, the lower portion of the fuze-hole, b, fig. 14, is partially closed, by screwing into it a disk perforated with a small hole for the passage of the flame from the fuze. The spherical case-shot mostly used for field service is the 12-pounder; it contains about 80 bullets; its burst- ing charge is 1 oz. of powder ; and it weighs when fin- ished 11.75 lbs., — nearly as much as a solid shot of the game calibre. The rupture of a spherical case-shot may be made to take place at any point of its flight ; and in this re- spect it is superior to canister and grape-shot, which begin to separate the moment they leave the piece. 47. Bar-§iiot. Bar-shot consist of two hemispheres, or twa spheres, connected together by a bar of iron ; the motion of rotation which these projectiles assume in flight, renders them useful in cutting the masts and rigging of vessels ; but, as they are very inaccurate, they are only employed at short distances. They are very little used, however, at the present day. Cham-shot only differ from bar-shot in the mode of connection, which is a chain, instead of a bar. 48. Percussion bullets. Percussion bullets may be made by placing a small quantity of percussion powder, enclosed in a copper envelope, in the point of an ordinary rifle-musket bullet, or by casting the bullet around a small iron tube, which is afterward filled with powder and surmounted with a common percussion-cap. The impact of the bullet against a sub- Fig, 15, •* ° 84 PEOJECTILES. KITPTIJEE. stance no harder than wood is found to ignite the percussion charge or cap, and produce an effective explosion. These projectiles can be used to blow up caissons, and boxes containing anamunition, at very long distances. 49. Carcasse§. Carcasses are shells which have three additional holes, of the same dimensions as the fuze- hole, pierced at equal distances apart in their upper hemispheres, with their exterior openings tangent to the great circle perpendicular to the axis of the fuze- hole. The object of a carcass is to set fire to wooden structures, by the flame of the burning composition which issues through the holes. CHAEGE OF EUPTUKE OF SHELLS. 50. Plane of rupture. Suppose the cavity of the shell to be spherical, and concentric with the exterior. As soon as the enclosed charge of powder is inflamed, the gases developed expand into the cavity, and the expansive force increases until it is sufficient to over- come the tenacity of the metal, and produce rupture ; which will take place in the direction of least resistance, or foUovnng a surface composed of lines normals to the two surfaces. Let i? be the radius of the exterior, and r the radius of the interior surface ; 0, the common centre of the two spheres ; T^ the tenacity of the material of which the sphere is composed ; and ^, the pres- Kg. 16. sure on a unit of surface to overcome the tenacity of the metal. PLANE OF EUPTXJEE. 85 Let G be the radius of the circle of rupture on tlie interior surface. From the known properties of gases, the pressure exercised on the area of this circle to pro- duce rupture is equal to the components of all the nor- mal pressures acting on the spherical segment of which it is the base, taken perpendicularly to the plane of this circle ; therefore t^pG''' is the pressure of the gases which tends to break the sphere. Under this supposition, rupture should follow the surface of the frustum of a cone of which this circle is the smaller base. The surface of this frustum is equal to the differ- ence of the surfaces of two cones whose common apex is at the centre of the sphere. The base of the smaller is 27r(7, and its slant height t ', its surface therefore is equal to ttCV, The surface of the larger cone, whose generatrix is the radius of the exterior sphere, will be to the smaller as R' is to r''. and therefore -nGr^: • their difference, or the area of the surface of rupture will be equal to trGrl—^ — 1 J. If the pressure of the gases acted normally to the sur- face of the fracture, or in the direction of the tenacity, this surface multiplied by T would give the total resist- ance, which should be equal to the pressure" of the gases ; but it acts obliquely, and to produce rupture should be increased by a quantity which depends on the law of increase of the resistance due to the angle which the pressure makes with the normal. Although we cannot measure this resistance, it must be admitted 86 PEOJECTILES. EUPTUEE. that the effort to overcome is greatest when the power is in the direction of the normal to the surface of rupture. We shall, therefore, have the relation, Or, In this expression the value of 6 is unknown ; but it is easy to be seen that it diminishes as the direction of the pressure approaches the normal, and when they coincide 6 becomes 0. At the same time G increases, and the value of jt? diminishes, until C becomes equal to /", its maximum value. Therefore, the section of easiest rupture of a hollow sphere passes through a great circle, and the pressure which is in equiUbrio with the tenacity of the metal, will be given by the fore- going formula, by making 6'==r, and cJ=0; it will then become. When the pressure is less than this value of p, the sphere will resist its charge of powder; when it is greater than this value, the sphere will burst. The density of the gaseous products of the powder necessary to burst the sphere can be easily found by Erumford's formula : Atmos. i?= 1.841 (905c^)i+"-5«=^; but d, or the density of the gaseous products, is equal LOSS OF GAS. 87 to their weight, or the weight of the bursting charge, divided by the interior space of the sphere. , w d=- r. Or, "i^' 51, Loss oi gas by fuze-hole. This loss of force by the fuze-hole may be ascertained with sufficient accuracy, provided we know from actual experiment the amount of the loss from the fuze-hole of any one shell. Let JR, and r be the exterior and interior radii of a spherical projectile ; T, the tenacity of the metal ; *', the radius of the fuze-hole ; ?/;', the weight of powder neces- sary to burst it under the supposition that there is no loss of force at the fuze-hole ; w, the weight of powder that is actually required to burst it. By the preceding formulas we obtain the value of w'; w—w' is therefore the amount of loss by the fuze-hole. Take another pro- jectile, and let w' represent the charge which is neces- sary to burst it, under the supposition that there is no loss, and w^ the weight that is found by experiment necessary to burst it; w, — w[ will represent the loss. "We are at liberty to suppose the loss from the two fuze-holes is proportional to the size of the holes, and the density of the gases at the moment of rupture ; we shall, therefore, have this proportion, w—w' : w,—wl :: i^d: ifd,. i^d Or, w=:.w' ^{w—w;)^—. Prom the experiments made at Metz in 1835, it was shown that this mode of estimating the loss of force by 88 PROJECTILES. FABRICATION. the faze-hole, was sufficiently exact for practical pur- poses. FABKICATION OF PROJECTILES. 52. Materials. Shot and shells should be made of gray or mottled iron, of good quality. SpTierical case-shot should be made of the best quality of iron, and with peculiar care, in order that they may not break in the gun. All projectiles should be cast in sand and not in iron moulds, as those from the latter are generally not spher- ical in form, nor uniform in size; they are also full of cavities, and are cracked by being heated. Sand. The sand used should be silicious, of an angu- lar grain, and moderate degree of fineness. It should be mixed with a sufficient quantity of clay, so that, when slightly moistened, it will retain its shape when pressed in the hand. Pattern. The pattern of a spherical projectile is com- posed of two hollow cast-iron hemispheres, which unite in such a manner as to form a perfect sphere; on the interior of each hemisphere is fastened a handle to enable the operator Fig. IT. to draw it from the sand when the half-mould is completed. The flasks which contain the mould are made of cast iron, in two equal parts united at their larger bases. Moulding. This operation is performed by placing the flat side of one of the hemispheres on the moulding- board, and covering it with a flask. Sand is then PATTEEN. 89 poured into the flask, filling up the entire space between it and the hemisphere, and well rammed. The flask is then turned over, the hemisphere is withdrawn, and the entire surface of the sand painted with coke-wash, and dried. The remaining half of the mould is formed in the same way, except that a channel foi; the introduction of the melted iron is made by inserting a round stick in the sand before it is rammed, and withdrawing it afterward. To secure strong metal and a homogeneous casting for large size solid shot, they are cast in a string, one above the other, with a large sinking head and connecting branches. They are afterwards cut apart and turned dowu to the required shape and size. Thi-ee 20-inch and four 15-inch shot may be cast in this manner. Hollow projectiles. Thus far, the operation of mould- ing and casting solid and hollow projectiles are the same. The cavity of a hollow projectile is made by in- serting a core of sand, which is formed around a stem fastened into the lower half of the mould. The stem is hollow, and perforated with small holes to allow of the escape of steam and gas generated by the heat of the melted metal. It is also made of iron, but that part of it which comes in contact with the melted ii'on, and forms the fuze-hole, is coated with sand. In pouring the melted iron into the mould with the ladle, care should be taken to prevent scoria and dirt from entering with it ; and, for this purpose, the sur- face should be skimmed with a wooden stick. Before the iron is fairly cooled, the flasks are open- ed, and the sand knocked from the castings. After this, the core is broken up. and knocked out, and the in- terior surface cleaned by a scraper. The sinking head 90 PKOJECTILES. ESrSPECTION. and otter excrescences are knocked off, and tlie surface smoothed in a rolling-barrel, or with a file, or cliisel, if necessary. The fuze-hole is then reamed out to the proper size, and the projectUe is ready for inspection. INSPECTION OF PROJECTILES. 53. Object of inspection. The principal points to be observed in inspecting shot and shells are, to see that they are of proper size in all their parts ; that they are made of suitable metal; and that they have no defects, concealed or otherwise, which will endanger their use, or impair the accuracy of their fire. As it would be impracticable to make all projectiles of exact dimensions, certain variations are allowed in the fabrication. See Ordnance Manual. Inspection of shot. The instruments are one large and one small gauge, and one cylinder gauge ; the cylin- der gauge has the same diameter as the large gauge, it is made of cast iron, and is five calibres long. There are also, one hammer with a conical point, six steel punches^ and one searcher made of wire. The shot should be inspected before they become rusty ; after being well cleaned, each shot is placed on a table and examined by the eye to see that its surface is smooth, and that the metal is sound and free from seams, flaws, and blisters. If cavities or small holes appear on the surface, strike the point of the hammer or punch into them, and ascertain their depth with the searcher ; if the depth of the cavity exceed 0.2 inch, the shot is rejected ; and also if it appear that an at- tempt has been made to conceal such defects by filling them up vnth nails, cement, &c. INSPECTION-. 91 The shot must pass in every direction, through the large gauge, and not at all through the small one ; the founder should endeavor to bring the shot up as near as possible to the large gamge, or to the true diam- eter. After having been thus examined, the shot are pass- ed through the cylinder gauge^ which is placed in an in- clined position, and turned from time to time, to pre- vent its being worn into furrows ; shot which slide or stick in the cylinder are rejected. Shot are proved by dropping them from a height of twenty feet on a block of iron, or rolling them down an inclined plane of that height, against another shot at the bottom of the plane. The average weight of the shot is deduced from that of three parcels of twenty to fifty each, taken indiscrim- inately from the pile ; some of those which appear to be the smallest should also be weighed, and they are rejected if they fall short of the weight expressed by their calibre, more than one thi/rty-second part. They almost invariably exceed that weight. Inspection of grape and camister shot. The dimen- sions are verified by means of a large and small gauge, attached to the same handle. The surface of the shot should be smooth, and free from seams. Inspection of hollow projectiles. The inspecting, in- struments are a large and small gauge for each calibre, and a cylinder gauge for shells of eight inches and under. Calipers for measuring the thickness of shells at the sides. Calipers to measure the thickness at the bottom. 92 PROJECTILES. INSPECTIOH. Gauges to verify the dimensions of the fuze-hole, and the thickness of the metal at the fuze-hole. A pair of liand-bellows ; a wooden plug to fit the fuze-hole, and bored through to receive the nozzle of the bellows. A hammer; a searcher ; a cold chisel ; steel punches. Inspection. The surface of the shell and its exterior dimensions, are examined as in the case of shot. The shell is next struck with the hammer, to judge by the sound whether it is free from cracks ; the position and dimensions of the ears are verified ; the thickness of the metal is then measured at several points on the great circle perpendicular to the axis of the fuze-hole. The diameter of the fuze-hole, which should be accurately reamed, is then verified, and the soundness of the metal about the inside of the hole is ascertained by inserting the finger. The shell is now placed on a trivet, in a tub contain- ing water deep enough to cover it nearly to the fuze- hole ; the bellows and plug are inserted into the fuze- hole, and the air forced into the shell ; if there be any holes in the shell, the air will rise in bubbles through the water. This test gives another indication of the soundness of the metal, as the parts containing cavities will dry more slowly than other parts. The mean weight of shells is ascertained in the same manner as that of shot. Shot and shells rejected in the inspection, are marked with an X made with a cold chisel — on shot near the gate, and on shells near the fuze-hole. PKESEEVATION. — SPILING. 93 PEESERVATION AND PILING OF BALLS. 54. i^ackering. Projectiles should be carefully lack- ered as soon as possible after they are received. When it is necessary to renew the lacker, the old lacker should be removed by rolling or scraping the balls, which should never be heated for that purpose. Piling. Balls should be piled according to kind and calibre, under cover if practicable, in a place where there is a free circulation of air ; to facilitate which, the piles should be narrow if the locality permits ; the width of the bottom tier may be from twelve to fourteen balls, according to the calibre. Prepare the ground for the base of the pile by rais- ing it above the level of the surrounding ground, so as to throw off the water ; level it, ram it well, and cover it with a layer of screened sand. Make the bottom of the pile with a tier of unserviceable balls, buried about two-thirds of their diameter in the sand ; this base may be made permanent ; clean the base well, and form the j)ile, putting the fuze-holes of the shells downward, in the intervals^ and not resting on the shells below. The base may be also made of bricks, concrete, stone, or with borders and braces of iron. 55. To &ati tlie Maimber of balls in a pile. Multiply the sum of the number of halls in the three parallel edges ly one-third of the number in a triangular face. In a square pile, one of the parallel edges contains but one ball; in a triangular pile, two of the edges have but one ball in each. 94 PEOJECTILES. — ROCKETS. Tlie number of balls in a triangular face is -^- — ] n being the number in tlie bottom row. The sum of the three parallel edges in a triangular pile is 7^+2 ; in a square pile, 2n-\-l; in an oblong pUe, Q]S/'-\-2n—2 ; iV^ being the length of the top row, and n the width of the bottom tier; or 3m— w+l; m being the length, and n the width of the bottom tier. If a pile consist of two joined at right angles, calcu- late the contents of one as a common pile, and the other as a pUe of which three parallel edges are equal. THEOEY AND CONSTEUCTION OF EOCKETS. 56. structure, A rocket is a projectile which is set in motion by a force residing within itself; it therefore performs the two-fold function of piece and projectile. It is essentially composed of a strong case of paper or wrought iron, enclosing a composition of nitre, charcoal, and sulphur — the same as gunpowder, except that the ingredients are proportioned for a slower rate of com- bustion. If penetration and range be required, its head is surmounted by a solid shot; if explosion and iacen- diary effect, by a shell or spherical case-shot, to which is attached a fu.ze, which is set on fire when it is reached by the flame of the burning composition. The base is perforated by one or more vents for the escape of the gas generated within, and sometimes with a screw-hole to which a guide-stick is fastened. The disposition of the different parts will be readily understood by reference to the subjoined figure, which MOTION. 95 represents a section tkrough tlie long axis of a Congreve rocket. Kg. 18. 57. Motion. A rocket is set in motion by tke reaction of a rapid stream of gas escaping tkrougli its vents. If it be surrounded by a resisting medium, tke atmosphere for instance, the particles of gas, as they issue from the vent, will impinge against and set in motion certain par- ticles of air, and the force expended on the inertia of these particles will react and increase the propelling force of the rocket. It follows, therefore, that, though a rocket will move in vaciLO^ its propelling force will be increased by the presence of a resisting medium. Whether the effect wiU be to accelerate the rocket de- pends upon the relation between the resistance which the medium offers to the motion of the gas, and that which it offers to the motion of the rocket. Vent. As the rate of combustion of the composition is independent of the pressure of the gas in the bore, it follows, that if the size of the vent be contracted, the flow of gas through it will be accelerated. The strength of the case, and the friction of the gas, which increases as the vent diminishes, alone limit the reduction of the size of the vent. For vents of the same size, but oi different shapes, that one which allows the gas to escape most freely, will be most favorable to the flight of the rocket. A conical form of vent, with the larger orifice next to the bore, will allow the gas to escape more rapidly than 96 PEOJECTILES. EOCKETS. one of cylindrical form. This may be shown by burn- ing portfire composition in tubes with different-shaped vents. It will be found that the sparks from a conical vent will be thrown much higher than those from a cylindrical vent ; the relative heights depending on the slope of the sides of the conical vent. Bore. As the composition of a rocket burns ia parallel layers of uniform thickness, the amount of gas generated in a given time, or the velocity of its exit from the case, depends on the extent of the inflamed surface. Experience shows that to obtaia the required sur- face of inflammation, it is necessary to form a long cavity in the mass of the composition. This cavity is called the hore. In small rockets, the bore is formed by driving the composition around a spindle which is after- ward withdrawn ; but in the large ones, the composition is driven into the case in a solid mass by a powerful hydrostatic press, and then bored out with a bit. In all rockets the bore should be concentric with the case ; its shape should be made conical to facilitate the draw- ing out of the spindle, and to diminish the strain on the case near its head, by reducing the amount of surface where the pressure on the unit of surface is greatest. Nature of movement. Suppose the rocket in a state of rest, and the composition ignited ; the flame imme- diately spreads over the surface of the bore, forming gas, which issues from the vent. The escape is slow in the first moments, as the density of the gas is slight ; but as the surface of the inflammation is large compared to the size of the vent, the gas accumulates rapidly, and its density is increased until the velocity of the escape GUIDING PEINCIPLE. 97 is sufficient to overcome the resistances whicli the rocket offers to motion. These resistances are, inertia, friction, the component of weight in the direction of motion, and, after motion takes place, the resistance of the air. The constant ;^ressnre on the head of the "bore accel- erates the motion of the rocket until the resistance of the air equals the propelling force ; after this, it will remain constant until the burning surface is sensibly- diminished. When the gas ceases to flow, the rocket loses its distinctive character, and becomes, so far as its. movement is concerned, an ordinary projectile. The increase in the siuface of combustion whereby more gas is developed in the same time, and the dimi- nution in the weight of the remaining composition, cause the point of maximum velocity to be reached with increased rapidity. If the weight of the rocket be increased, the instant of maximum velocity will be pro- longed, but the amount will remain the same. A change in the form of the rocket which increases the resistance of the air, will have the effect to diminish the maximum velocity. The maximum velocity of French rockets, and the- distances at which they are attained, are given in the following table : — CALIBEB. DISTANCE. MAZM. TELOCITY. 21 inches, 134 yds. 278 yds. 3|- " • 141 " 370 " According to the calculations of Piobert, for small rockets it takes about f second for the gas to attain its maximum velocity of 850 yds. 58. Ouidins principle. The propelling force of a 7 98 PEOJECTILES. EOCKETS. rocket changes its direction witli the axis along which it acts ; it follows, therefore, that without some means of giving stability to this axis, the path described will be very irregular, so much so, at times, as to fold upon itself; and instances have been known where these pro- jectiles have returned to the point whence they started. An example of this irregular motion may be seen in "serpents," a species of small rockets without guide- sticks. The two means now used to give steadiness to the flight of a rocket are, rotation, as in the case of a rifle- ball, and the resistance of the air, as in an arrow. Hale's system. The first is exemplified in Hale's rocket, where rotation is produced around the long axis by the escape of the gas through five small vents situ- ated obliquely to it. In his first arrangement, the in- ventor placed the small vents in the base, surrounding the large central vent, so that the resultant of the tan- gential forces acted around the posterior extremity of the axis of rotation. In 1855, this arrangement was changed by reducing the number of the small vents to three, and placing them at the base of the head of the rocket. The rocket thus modified, and shown in fig. 20, is the one now used by the United States government for war purposes.* * A still later improvement in Hale's rocket consists in screwing a cast-iron piece (a) into the bottom of the case, ■which is perforated with three vents. A corresponding t\J^^ "''-' d^ :: and B^ d'^:: or D d :: and I) d' :: V V V v' From these last two proportions we have D ; JD or D—d JD- D- D- -d -d' -d' V: F- V: V- V-^ : -v' V- In which, D, d, and d' represent the diameters of three balls, and V, v, v' their initial velocities, respectively. If D equal the diameter of the bore, D—d is the wind- 126 CAWNON". WINDAGE. age of the ball whose diameter is d^ and D—d' is tLe windage of the ball whose diameter is d'. If we mul- tiply the extremes and means of the last proportion, and divide the resulting equation by V (^D—d), we shall have the expression V— v' _,j, -,,. V—v V—v By making m=-p=--rj^— — ^ ithe equation becomes V-v'=Vxin{I)-d'). This equation expresses the relation between a certain windage, Z>—(i' and the loss of velocity due to that windage, or V—v'. In a series of experiments made by Major Mordecai, with the ballistic and gun pendulums, it was found that m was constant for all values of D—d' that would be likely to arise in service. From this it follows that V —v' is proportional to D—d'; or, in other words, that the loss of velocity hy windage is proportional to the windage. When the charge of powder was varied, it was found that the absolute loss of velocity by a given increase of windage, was very nearly the same for all the charges used. It follows from this that the proportional loss is less for the higher charges. Both the absolute and relative loss of velocity by a given difference of windage (say one-tenth of an inch) jTicrease as the calibre of the piece decreases. From the foregoing, it may be stated, tJiat the loss of velocity by a given tvindage, is directly as the windage., and irmersehj as the diameter of the bore, very nearly. LENGTH OF BOEE. 127 The loss of velocity of a 24-pdr. ball by a windage of -^, and a charge of 6 lbs. of powder, is 9 per cent. LENGTH OF BORE. 92. Ancient tsieory. The slow rate of burning of mealed powder, which was originally used in cannon, led to the belief that the longest pieces gave the gi-eat- est ranges. In spite of much experience to the con- trary, this belief was entertained, even after gunpowder received its granular form; and several pieces were made of enormous length, with the expectation of real- izing corresponding ranges. A culverin was cast during the reign of Charles V. which was 58 calibres long, and fired a ball weighing 36 lbs.; but on trial, this piece was found to have actually less range than an ordinary 12-pdr. gun. The experiment of reducing its length, by successively cutting it off to 50, 44, and 43 calibres, was tried, and it was found that the range increased at each reduction until it gained 2,000 paces. 93. What govermo the Icragtli. That the length of the bore has an important effect on the velocity of the projectile, will be readily seen by a consideration of the forces which accelerate and retard its movement in the piece. The accelerating force is due to the expansive effort of the inflamed powder, which reaches its maximum when the grains of the charge are completely converted into vapor and gas. This event depends on the size of the charge, and- the size and velocity of combustion of the grains. With the same accelerating force, the 128 CANNON". LENGTH OF BOEE. point at wHcli a projectile reaches its maximum velocity- depends on its density, or the time necessary to over- come its inertia. The retarding forces are — 1st. The friction of the projectile against the sides of the bore : this is the same for all velocities, but different for different metals; 2d. The shocks of the projectile striking against the sides of the bore : these will vary with the angle of in- cidence, which depends on the windage, and the extent of the injury due to the lodgment and balloting of the projectile ; 3d. The resistance offered by the column of air in front of the projectile : this force will increase in a certain ratio to the velocity of the projectile and length of the bore. As the accelerating force of the charge increases up to a certain point, after which it rapidly diminishes, as the space in rear of the projectile increases, and as the retarding forces are constantly opposed to its motion, it follows, that there is a point where these forces are equal and the projectile moves with its greatest velocity; it also follows that after the projectile passes this point, its velocity decreases until it is finally brought to a state of rest, which would be the case in a gun of great length. 94. Experitmemts to determine it. Elaborate experi- ments have been made in this country and abroad, to determine accurately the influence which the length of the piece exercises on the velocity of its projectile. The curves in the accompanying figure show to the eye the relation existing between the different lengths of the bore of a 12-pdr. gun and the corresponding velocities, for charges of 2.2, 3.3, and 4.4 lbs. The ordinates represent the lengths of the bore in CONOLUBIONS. 129 calibres, and tlie abscissas represent the velocities, as determined by tlie electro-ballistic pendulum. Length in calibres, 20.8 " 18.3 " 15.8 " 13.3 " 10.8 8.3 " 5.8 V e 1 o c i t i e s 2-2Ibs. 7-3Ibs. Av&Ibs. / ^ / / ' / / / / / / / y y ^ Pig. 31. An inspection of tbe figure shows tbat the velocity- increases with the length of the bore in a variable ratio, the increase of velocity for the short lengths being much greater than for the long lengths. The experiments made by Major Mordecai, some years before these, on a gun of the same calibre, show that the velocity increases with the length of the bore up to 25 calibres; but that the entire gain beyond 16 calibres, or an addition of more than one half to the length of the gun, gives an increase of only one-eigTiteenth to the effect of a charge of 4 lbs. 95. Conclusions. It follows from the foregoing, that the length of bore which corresponds to a maximum velocity, depends upon the projectile, charge of powder, and material of which the piece is made ; and taking the calibre as the unit of measure, it is found that this length is greater for small arms, which fire leaden pro- jectiles, than for guns which fire solid iron shot, and greater for guns than for howitzers and mortars, which fire hollow projectiles. 130 CAWNON. CHARGE. For tlie same charge of powder, it may be said that the initial velocity of a projectile varies, nearly, with the fourth root of the length of the hare, provided the varia- tion in length he small. CHARGE. 96. Maximum cbarge. By increasing the charge of powder of a fire-arm, the greater and (in consequence of the wedging of the unburned grains among each other) the more difficult will be the mass to be set in motion ; the space between the front of the charge and the muzzle will be diminished ; and a larger number of grains will be thrown out unconsumed. It is evident, therefore, that the effect of a charge of powder on a projectile should not increase with the size of the charge; and experiment shows that beyond a certain, point, an increase of charge is actually accompanied with a loss of velocity. The charge corresponding to this point is called the maximum charge. The following are the results of experiments made in France on a 36-pounder gun, of 16 calibres in length: Charge, lbs., . . 36, 42, 49, 56, YO, 77. Initial velocity, feet, 1,320, 1,170, 950, 493, 454, 191. It will therefore be seen that an excess of charge is almost as injurious to the velocity of a projectile, as an excess of length of bore. 97. Effects on recoil. Trials made at Turin show that the recoil, and consequently the strain on the gun and carriage, increase in a more rapid ratio than the charges. MATERIALS. 131 viz.: 14 lbs. of powder gave a recoil of TO inches; 15 lbs,, 72 inches; 16 lbs., 74 inches; 18 lbs., 100 inches. 98. Effect of length of bore on maximum eharge. All experience proves that the longer a piece is, in terms of its calibre, the greater will be the maximnm charge in proportion to the weight of the projectile. For heavy- cannon, 19 to 20 calibres long, the maximum charge may- be stated to be i the weight of the projectile ; and for light cannon of the same length, J- to f of this weight ; the increase of range for charges above ^ the weight of the projectile, being very small. 99. Most suitable charge. A charge of ^ the weight of the prcflectile, and a bore of 18 calibres, is the most favorable combination that can be made in smooth- bored cannon,, to obtain the greatest range "with the least strain to the carriage. In the early days of artillery, when dust instead of grained powder was used in cannon, the weight of the charge was equal to that of the projectile ; after the introduction of grained powder, it was reduced to -I, and in 1740 to i, this weight. MATEEIALS. 100. Requirememts. Before discussing the exterior form of cannon, it is necessary to study the nature of the materials of which they are composed. The selection of a suitable material is a very important consideration in the construction of cannon, in conse- quence of the great difficulty of obtaining any one. that possesses all the qualities required of it. 132 CANNON. — MATEEIALS. The qualities necessary in cannon-metals are, strength to resist tlie explosion of the charge, weight to overcome severe recoil, and ha/rdm£ss to endure the bounding of the projectile along the bore. 101. stremgtsi. The term strength, as applied to a cannon-metal, should not be confined to tensile strength alone, which expresses the ability of a substance to resist rupture from extension produced by a simple pressure, as a weight, but should embrace a knowledge of its elasticity, ductility, and crystalline structwe, which affect its power to resist the enormous and oft-repeated force of gunpowder — a force which resembles a blow, in the rapidity of its application. Elasticity. It has been shown by experirnent, that the feeblest strains produce permanent elongation or compression in iron ; and the same is probably true of aU other materials. Perfect elasticity cannot, there- fore, be found in solids, although different substances possess it in different degrees. It follows that each discharge, however small, must impair the strength of a cannon, and an ordinary discharge, repeated a suf- ficient number of times, will burst it. In the selection of a durable cannon-metal, it is necessary to know, not only the ultimate rupturing force, but also the relation between lesser forces, and the extension and compression produced by them, and the permanent extension, or compression, which remains after these forces are withdrawn, or what is technically known as the " permanent set." This knowledge will be useful in regulating the charge of a cannon to suit the required endurance. Ductility. Ductility is the property which a metal MATERIALS. 133 possesses of changing its form, without rupture, after it has passed its elastic limit, under the operation of ex- traneous forces, and, for present purposes, may be con- sidered as opposed to brittleness. Of two metals that possess the same tensile strength and elasticity, it is evident that it will require more " work" to rupture the one which possesses the greatest amount of ductility. Crystalline strucPure. The size and arrangement of the crystals of a metal, have an important influence on its strength to resist a particular force. This arises from the fact that the adhesion of the crystals, by the contact of their faces, is less than the cohesion of the particles of the crystals themselves, and that, consequently, rup- ture takes place along the larger, or principal crystalline faces. A metal will be strongest, therefore, when its crystals are small, and the principal faces are parallel to the straining force, if it be one of extension, and perpen- dicular to it, if it be one of compression. The size of the crystals of a particular metal depends on the rate of cooling of the heated mass : the most rapid cooling gives the smallest crystals. Practically, there is a limit to the rate of cooling of certain metals ; cast iron, for instance, is supposed to change its nature by losing a portion of its uncombined carbon, when suddenly cooled, as in iron moulds. The position of the principal crystalline faces of a cooling solid, is found to be parallel to the direction in which the heat leaves it, or in a direction perpendicular, to the cooling surface. The result of this arrangement of crystals is to create 134 CANNON. MATEEIALS. H Fig. 32. planes of weakness where tlie different systems of crys- tals intersect. Figure 32 represents sections of the cylinders of two hydraulic presses, used in the construc- tion of the Britannia Bridge, The bottom of No. 2, which was flat, gave way along the lines of weakness A B and C D, while No 1, which was hemi- spherical, and present- ed no lines of weak- ness, resisted all the pressure applied to it. The effect of this law on the strength of cannon seems to have been first noticed by Mr. Mallet ; and its truth has been confirmed in several instances by Captain Eod- man, of the ordnance department, who finds that- radial specimens are more tenacious than those cut ta/ngentidUy from the same gun. 102. Effect of cooling. All Solid bodies contract their size in the operation of cooling. It follows, therefore, that if the different parts of a body cool unequally, they will contract unequally, and the body will change its form, provided it be not restrained by the presence of a superior force ; if it be so restrained, the contractile force will diminish the adhesion of the parts by an amount which depends on the rate of cooling of the different parts, and the contractibility of the metal. This is an important consideration in estimating the strength and endurance of cannon, particularly those made of cast iron, as will be seen by examining the form of the casting and the method of cooling it. The general form of the casting is that of a solid frus- tum of a cone ; it is, therefore, cooled from the exterior, EFFECT OF COOLING. 135 whicli causes the tHn outer layer to contract first, and force the hotter and more yielding metal within, toward the opening of the mould. Following this, the adjacent layer cools, and tends to contract ; but the exterior layer, to which it coheres, has become partially rigid, and does not fully yield to the contraction of the inner layer. The result is, the cohesion of the particles of the inner layer is diminished by a force of extension, and that of the outer layer increased by a force of compression. As the cooling continues, this operation is repeated until the whole mass is brought to a uniform tempera- ture ; and the straining force is increased to an extent which depends on the size and form of the mass, the rapidity with which it is cooled, and the contractibUity of the' particular metal used. All cannon, therefore, that are cooled from the exte- rior are affected by two straining forces — ^the outer por- tion of the metal being compressed, and the interior extended, in proportion to their distances from the nevr tral axis, or line composed of particles which are neither extended nor compressed by the cooling process. The effect of this unequal contraction may be so great as to crack the interior metal of cast-iron cannon, even before it has been subjected to the force of gunpowder; and chilled rollers, which are cooled very rapidly by casting them in iron moulds, have been known to split open longitudinally, from no other cause than the enor- mous strains to which they are thus subjected. The strain produced by the action of a central force, as gunpowder acting in a cannon, is not distributed equally over the thickness of metal. Barlow shows that it diminishes as the sqna/re of the distance from the 136 CANKON. — MATEEIALS. centre increases* It follows from this, that the sides of a cannon are not rent asunder as by a simple tensile force, but they are torn apart like a piece of cloth, com- mencing at the surface of the bore. This is confirmed by experience; for the inner portion of the fractured surface of a ruptured gun, is found to be stained with the smoke of the powder, while the outer portion is un- touched by it. It will thus be seen that the effect of ordinary cooling is, to diminish the strength and hardness of the metal of cannon at, or near, a point where the greatest strength and hardness are required, i. e., at the surface of the bore. CircwmstoMces affecting it. The strains produced by unequal cooling increase with the diameter of the cast- ing, and the irregularity of its form. This explains the great difficulty which is found in making large cast-iron cannon proportionally as strong as small ones ; and also, how it is that projections, like bands, mouldiugs, &c., injure the strength of cannon. It also explains why cannon made of " higlH'' cast iron, or cast iron made more tenacious by partial decarbonization, are not so strong as cannon made of weaker iron ; for it is well known that such iron contracts more than *the latter in cooling, and therefore produces a greater strain of extension on the surface of the bore. RodmarHs plan. The foregoing considerations led Captain Eodman to propose a plan for cooling cannon from the interior, hoping thereby to reverse the strains * From this law it can be shown that a piece with a thickness of metal equal to one calibre, experiences nine times greater strain on the surface of the bore than on the exterior. WEIGHT, HAEDNESS, ETC. 137 produced by external cooling, and make tliem con- tribute to the endurance rather tlian to tlie injury of the piece. The method employed is, to carry off the internal heat by passing a stream of water through a hollow core, inserted in the centre of the mould-cavity before casting, and to surround the flask with a mass of burning coals to prevent too rapid radiation from the exterior. Extensive trials have been made to test the merits of this plan; and the results show that cast-iron cannon made by it are not only stronger but are less liable to enlargement of the bore from continued firing. Indications were shown, however, in these and in other trials, that the strains produced by unequal cool- ing are modified by time, which probably allows the particles to accommodate themselves, to a certain extent, to their constrained position, as in the case of a bent spring or hoop. 103. "Weight. When a material possesses great strength, but cannot be easily wrought into a heavy mass, it is customary to diminish the recoil by applying an ex- traneous weight to the piece, or by some contrivance for increasing the weight or friction of the carriage. It is evident that these methods want that unity and solidity which are necessary to great endurance in can- non. 104. Hari-9 of flanges, or giving a peculiar form to the projectile. 2d, JBy expansion. 3d. By compression,. ist Glass. Solid flanges projecting from tlie body of a projectile and so shaped as to fit the rifling of the bore, were the means first used to communicate the rifle- motion in cannon. These projections were in the form of ribs or rounded buttons of the same substance as the body of the projectile. This, however, being of a very unyielding nature, frequently led to the bursting of the piece, and buttons of zinc, copper, or bronze, firmly se- cured in mortices in the projectile, were adopted. These buttons were arranged in rows of two or more in such a way that each row entered freely into a correspond- ing groove of the rifling, in loading. Nearly all of the military powers of Europe have adopted the button system of rifling, in one shape or other. If the bore of a gun be cut into a spii-al form with a polygon, or curve for its base, and the projectile bo shaped to fit it, it is evident that the projectile will re- ceive the rifle-motion when fired. The Whitworth and Lancaster cannon are rifled in this manner, the cross sec- tion of the former being a hexagon with rounded coi-- ners, while the latter is an ellipse. The principal advantages of the foregoing modes of rifling are that the projectiles are strong and that the rifle-motion is communicated to them with great cer- tainty and regularity. They are, howevei-, liable to pro- duce a strain on the gun, and unless great care is taken to clean the bore, are sometimes difficult to load. Id Glass. In projectiles of the second class the body 170 CANNON. — RIFLED. is composed of a hard raetal, as cast-ii'ou, and there is attaclied to it, genei-ally at the base, a cup, band, or otlier arrangement of soft metal, which is expanded by tlie action of the charge into the grooves of the gun when fired. Expanding projectiles are exclusively used in the U. S. service, jiriucipally for the reason that they are easy to load and do not clog the grooves in a man- ner to ovei-strain the piece. Expanding projectiles of different patterns can be generally used in the same gun, a point of great importance during the late war when the service depended on private manufacturers for its supply. Expanding projectiles cannot be fired with as heavy a charge of powder as others, for fear of break- ing, nor are they so sure to receive the rifle-motion. Parrott, Hotchkiss, Schenkle, Dyer, and many other projectiles belong to this class. Zd Class. Projectiles of the 3d class are principally used in breach-loading cannon. They are generally cov- ered with soft metal in such manner as to enter the chamber freely. The bore being smaller than the pro- jectile, a portion of the soft metal covering is forced into the grooves, thus compelling the projectile to follow the direction of the rifling. Very few rifle-cannon are now made on the breech- loading principle, as they are necessarily weaker than muzzle-loading guns. Centering System. In consequence of windage, whicli is necessary in all muzzle-loading guns, the axis of the projectile does not always coincide with that of the bore in firing. This leads to inaccuracy of fire. A projectile is said to be centered when the grooves of the rifling are so constructed as to bring the axis of UNIFORM GROOVE, 171 the projectile in line with that of the bore when the piece is fired. There are several ways of accomplishing this; the most noted perhaps is the Armstrong " shunt rifling," described in the appendix. 131. Form of grooTe. The form of a rifle groove is determined by the angle whicli the tangent at any point makes with the corresponding element of the bore. If the angles be equal at all points, the groove is said to be uniform. If they increase from the breech, to the muzzle, the grooves are called increasing^ if the reverse, decreasing grooves. Twist is the term generally used by gun-makers, to express the inclination of a groove at any point, and is measured by the length of a cylinder corresponding to a single revolution of the spiral ; this, however, does not convey a correct idea of the inclination of a groove. A correct measure of the inclination of a rifle groove at any point, is the tangent of the angle which it makes with the axis of the bore ; and this is always equal to the circumference of the hore di/vided ly the length of a single revolution of the spiral^ measured in the direction of the axis. 132. Unifform groove. To construct the development of a uniform groove, let A Jihe the base of a rectangle, equal to the circumference of the bore; B C, the height equal to the length of a single revolution of the spiral, measured on the axis of the bore. The diagonal .^ 6^ is the development 6f an entire revolution of the required groove. Kg, 40. On the line A D lay off the distance 172 GAI\WON. EIFLED. A d, equal to the length of tlie bore ; at d erect a perpendicular, and the line A c will be that portion of the development of the groove which lies on the surface of the bore. 133. Variable groove. Variable grooves are con- structed by Avrapping a curve around the surface of the bore. The curve generally selected for this purpose, i:^ the arc of a circle. To construct the development of an increasing groove which shall be the arc of a circle : The known condi- tions of construction are the length of the bore, and the inclination, or twist, at the breech and at the muzzle. The quantity to be determined is the radius of the gen- erating circle. Suppose the problem solved, and let £ P represent the element of the bore passing through the extremity of the groove at the muz- zle; P (7, the tangent to the groove at this point; A the starting point of the curve ; and A D the tangent Kg. 41. to the groove at this point. The angle of the tangent and element at the breech, is generally made zero, and is so considered in this par- ticular case. The perpendiculars at A and P are radii of the required circle, and their intersection, (9, will be its centre. To determine the length of the radius A 0, and the versed sine of the arc A P : From the nature of a circle, the angle GPB=AOP ; BO^ ^ „ / ' ® ' 't&n. POP' and OP=i/pp^-\-£0\- or, by substituting' for: ^6> METHOD OF CUTTING- GROOVES. 173 7? pa its value, 0P=.^/ ^P^+___^_^, and ^^= BP'' BP" BP ian^CPB tan.BOP' 134. Method of cntting grooves. The practical metliod of cutting grooves in cannon is essentially tlie same as in small arms. It consists in moving a rod, armed witli a cutter, back and forth in the bore, and at the same time revolving ifc around its axis. If the velocities of translation and rotation be both uniform, the grooves will have a uniform twist ; if one of the velocities be vari- able, the grooves will be either increasing or decreasing, depending on the relative velocities in the two directions! 135. Comparative advantages. The comparative ad- vantages of uniform and variable grooves, depend dn the means used to connect them with the projectiles. If the bearing of the projectile in the grooves be long, and the metal of which it is made be unyielding, it will be unsafe, if not impracticable, to employ variable grooves ; and if the metal be partially yielding, a portion of the force of the charge will be expended in changing the form of that part of the projectile which projects into the grooves, as it moves along the bore. When the portion in the grooves is so short that its form will undergo but slight alteration, the increasing groove may be used with advantage, as it diminishes the friction of the projectile when it is first set in motion, and thereby relieves the breech of the piece of a portion of the enormous strain which is thrown upon it. If the twist be too rapid toward the muzzle, there will be danger of bursting the piece in the chase. 174 CXNNON. EIFLED. It is claimed by some, that the variable groove is well adapted to expanding projectiles with short bear- ing surfaces ; but the uniform groove, being more sim- ple in its construction, and nearly as accurate in its results, is generally preferred for military fire-arms, both large and small. 136. Wiimber, widtti, and shape of grooves. The width of a groove depends on the diameter of the bore, and the peculiar manner in which the groove receives and holds the projectile. "Wide and shallow grooves are more easily filled by the expanding portion of a projectile than those which are narrow and deep ; and the same holds true of cir- • cular-shaped grooves, when compared to those of angu- lar form. An increase in the number of grooves in- creases the firmness with which a projectile is held, by adding to the number of points which bear upon it. It has been suggested that rifle-cannon, intended for flanged projectiles, should have four grooves; as a greater number increases the difl3.culties of loading, and a lesser number does not hold the projectile with sufl&- cient steadiness. For expanding projectiles, an odd number of grooves is generally employed, for, as this places a groove op- posite to a land, less expansion will be required to fill them. The number of grooves used in the 3-inch field-gun is seven, and the number used in 4i-inch siege- guns is nine. The number of grooves in the 4-inch Arm- strong gun is ffty. 137. Initial velocity of rotation. Let V\>Q the ini- tial velocity of the projectile, or space which it would pass over in one second, in the direction of flight, INCLINATION OF GROOVES. 175 moving witL. the velocity "with whicli it leaves the piece, and I the distance passed over by the projectile in making one revolution ; therefore, -y- will be the number of revolutions in one second, and 27r— the angular velocity of the projectile at the muzzle. The velocity of rotation of a point on the surface is given by the expression, L in which r is its distance from the axis of motion, and w is the angular velocity. 138. lasclimatioii of grooves. The object of rifle- grooves being to communicate an effective rotary motion to a projectile throughout its flight, it remains to de- termine what velocity of rotation, or inclination of grooves, is necessary for different projectiles. The velocity of rotation will depend on the form and initial velocity of the projectile, the causes which re- tard it, and the time of flight ; therefore, tliiere is a par- ticular inclination of grooves which is hest suited to each calibre, form of projectile, charge of powder, and angle of f/re. It is proposed to investigate the effect of the length and calibre of the projectile, on the inclination of the grooves. 139. Effect of length. It has been noticed that if very long projectiles be fired from the rifle-musket, they are less accurate than the ordinary projectile, the length of Avhich is less than two calibres. Mr. Whitworth states that he has known a bullet twice this length, turn over 176 CANNON. RIFLED. end for end, witMn six feet of tlie muzzle of the Eng- lish, rifle-musket, the calibre of which is nearly the same as that of the American rifle-musket. This instability undoubtedly arises from the want of sufficient rotation around the long axis. What increase of angular velocity must, therefore, be given to com- pensate for a given increase of length of an oblong projectile? The resistance which a projectile offers to angular deflection, when rotating around a principal axis, is pro- portional to the moment of its quantity of motion taken with reference to this axis, or MWw, M being the mass, h radius of gyration, and w the an- gular velocity. Let this expression represent the moment of the quantity of motion around the long axis, and h^ and w^ the radius of gyration, and angular velocity, around a short axis, and suppose the angular velocities w and w^ to be such that the resistance to a deflection from the axes shall be equal, we have and by reduction, Ti Hence, if we determine by experiment the value of w, the angular velocity necessary to give proGticable sta- bility of rotation, we can determine the value of w„ and consequently the superior limit of the deflecting forces. Substituting the value of w^ in a similar expression for any other projectile, we can determine the angular EFFECT OF EESISTANCE OP THE AIE. 177 velocity, and from this the inclination of grooves neces- sary to give the second projectile steadiness in flight. The foregoing method of determining the relation between the lengths of two rifle-projectiles, and the in- clination of grooves necessary to give them equal stead- iness of flight, is true only under the supposition that they preserve throughout their range the relative an- gular velocities with which they started. It is neces- sary, therefore, to consider the causes which affect ro- tation. 140. Effect of resistance of the air. The cause which retards the rotary motion of a rifle-projectile, is the friction of the air on its surface; and its retarding effect will be equal to its moment divided by the moment of the projectile's quantity of motion. Lety be the friction on a unit of surface ; s, the sur- face of the projectile ; p, the distance of the resultant moment of the friction from the axis of motion ; k, the radius of gyration ; and v, the mean velocity of the pro- jectile during its flight. The pressure of the air on the projectile is nearly proportional to the square of its velo- city : f s v^ will therefore represent the friction on the projectile, and./ s v^ p will be its moment. The moment of the quantity of motion of the pro- jectile is MWw^ J/^ being the mass, and w the angular velocity. The expression for the angular retardation is, there- fore, fsv^p MwW To find the angular velocity that it is necessary to give to another projectile, that it may experience the 12 178 CANNON. EIFLED. same retarding effect, place this expression equal to a similar one, answering to this projectile, and we liave : Reducing, and recollecting tliat tlie surface is propor- tional to tlie square, and the mass to the cube of the mean diameter, we have : dliw~ dj&fw] or, v^p vfp, 111 ' on ' ' ■ — ' • '•• J/5;^ • d,hr Hence, if the angular velocity necessary for one rifle- projectile be known, the angular velocity necessary for another of similar form and material, but of different size, may be determined by calculation. Suppose the two projectiles to be round shot, and moving with the same mean velocity, through the same extent of trajectory, the proportion reduces to But the angular velocity is inversely proportional to the length of the twist ; it follows, therefore, tliat the " length of twisf of grooves^ for round shot, moving through equal lengths of trajectory, and with equal mean velocities, should he directly as the squares of their diameters. 141. Position of centre of gravity. The further the centre of gravity of a projectile is in rear of the cen- tre of figure, or resistance of the air, the greater will be the lever arm of the deviating force, and, consequently, the greater must be the inclination of the grooves, to INCLINATION OF GROOVES. 179 resist deviation. A conical projectile, of the same length and diameter, requires a greater inclination of grooves than a cylindrical projectile ; and the same will hold true of other forms, as they approach one or the other of these extreme cases. 142. limit of inclination. The friction of the pro- jectile as it passes along the grooves, increases with their inclination ; its effect will be to diminish the range, and increase the strain on the piece. It is easily to be seen that the inclination may be carried so far as to break the projectile, or rupture the piece. 143. Most suitable inclination. The inclination of grooves for a rifle-cannon, best suited to a given projec- tile, has not yet been determined by experience ; and the consequence is, that a wide diversity of " twists" is employed in different services, and by different experi- menters. Colonel Cavalli, in his experiments in Sweden, obtained good results from twists of one turn in 12 feet, and one turn in 35 feet, in a 32-pdr. gun ; and a still greater variety of twists have been employed in our own service. For a projectile one and a half diameters long, and 6-pdr. calibre, excellent practice has been obtained with a twist of 25 feet; and in a certain form of the Arm- strong gun, the twist is 12 feet for a bore 4 inches in diameter. The twist of the new wrought-iron rifle-gun for field service, is 10 feet, and the twist of the new siege gun is 15 feet. The calibre of the former is 3 inches, and the latter 4^ inches. 180 CANNON. — VAEIOUS USES OF. USES TO WHICH CANNON AEE APPLIED. Having discussed the general principles wMcli govern the construction of all cannon, it is now proposed to consider the peculiarities which arise from the uses to which the several kinds are applied. 144. Fieid-caunon. Field-cannon are intended to be used in the operations of an army in the field; they should, therefore, have the essential quality of mobility. They are divided into light and heavy pieces. The former are constructed to follow the rapid movements of light troops and cavalry. The latter are employed to follow the movements of heavy troops, to commence an action at long distance, to defend field-works and important positions on the field of battle, «fec. ; hence they are said to constitute " batteries of position." Formerly the light pieces of the field service were the 6-pdr. gun and 12-pdr. howitzer; and the heavy pieces were the 12-pdr. gun, and 24-pdr. and 32-pdr. howitzers. At the commencement of the late war in this country, these pieces were set aside for arming field works, block houses, etc., and their places were supplied with the light 12-pdr. gun (smooth bore) .and the 3-inch rifle-gun. The regulations prescribe that^ as a general rule, one-third of the pieces of a field-battery be rifles and the remainder smoothbores. Of course this proportion is subject to be modified by the character of the operations and the nature of the country. The country in which most of our late military operations were conducted, was either broken in surface or heavily wooded, and the most ef- fective fighting was done at moderate ranges, at which FIELD CANNON. 181 the light 12-pdr., with its heavy shell and case-shot, was found more destructive than the 3-iuch rifle-gun. Rifle-guns. The 3-inch ]ifle-gun is made of wrought- iron after a plan invented at the Phoenixville Iron Works, Penn. This plan consists simply in wrapping boiler plate around an iron bar so as to form a cylin- drical mass of a certain diameter. The whole is placed in a furnace and brought to welding heat and then passed between rollers to unite it solidly together. The trunnions are afterwards welded, or "jumped" on, and the piece is bored and turned to the proper size and shape. The form of this piece is shown in the accompanying figure, and is the same in its general character as all the guns of the Rodman pattern. Fig. 41 (a). The following are its principal weights, dimensions, etc. Weight, 820 lbs. Diameter of bore. 3 in. Length of bore, - 21^- diam. Number of grooves, - 7 Deptli of grooves, 0.075 in. Twist, - - 11 ft. Projectile, weight of - - 10 lbs. Powder, - 1 lb. The projectiles used are shells with time and percus- sion fuzes, and case and canister shot. Hotchkiss, 182 CANWOK. VARIOUS ITSES OF. Sclienkle, and Dyer projectiles are all suited to the rifling of this gun. A 3-inch Parrott rifle-gun, using Parrott projectiles, is also employed in the U. S. held service. This is a cast- iron piece reinforced with a band of wrought-iron, simi- larly to other guns of the Parrott system, (see appen- dix). 145. Napoleon Gun. In 1856 it was proposed to in- crease the power of the light and diminish the weight of the heavy field artilleiy, by the introduction of a sin- gle piece of medium weight and calibre, (see par. 76). Fig. 42. Form. The forni of the new piece is shown in fig. 42. It has no chamber, and should therefore be classed as a gun. Its exterior is characterized by the entire absence of moulding and ornament ; and in this respect it may be at once distinguished from the old field cannon. The first reinforce is cylindrical ; and it has no second reinforce, as the exterior tapers uniformly with the chase from the extremity of the first reinforce. The size of the trunnions and the distance between the I'imbases are the same as in the 24-pdr. howitzer, in order that both pieces may be transported on the same kind of carriage. Dimensions^ c&c. The diameter of the lore is that of a 12-pdr. The length of bore is 13| calibres. The weight is 100 times the projectile, or 1,200 lbs. The charge of JMOUNTArN- AND PEAIRIE CANNOir, 183 lX)wder is the same as for the heavy 12-pdrs. (pattern of 1840), or 2^ lbs. for solid and case shot, and 2 lbs. for canister shot. It has, therefore, nearly as great range and accuracy as the heaviest gun of the old sys- tem ; and, at the same time, the recoil and strain on the carriage are not too severe. The new gun and carriage weigh about 500 1))S. more than the 6-pdr. and carriage; still, it has been found to jiossess suflBcient mobility for the general purposes of light artillery. The effect of this change is to simplify the materiel of field artillery, and to increase its ability to cope with the rifle-musket, principally by the use of larger and more powerful spherical case-shot. The principal ob- jection to an increased calibre for light field-guns, is the increased weight of the ammunition, and the reduction of the number of rounds that can be carried in the am- munition chests. MOUNTAIN AND PRAIKIE CANNON. 146. MoHntain howitzer. Mountain artillery is de- signed to operate in a country destitute of carriage-roads, and inaccessible to field artillery. It must, therefore, be light enougli to be carried on pack-animals. The piece used for moun- tain service is a short, light 12-pdr. howitzer, weighing Kg. 43. 220 lbs. See fig. 43. The form of the chamber is cylindrical, and suited to a charge of \ lb. of powder. The projectiles are shells and case-shot. It is discharged from a low two- wheel carriage, which 184 CAKlSrON. SIEGE AND GAKBISON CANNON". serves for transportation whenever the ground will per- mit. When the piece i^ packed, the carriage is packed on a separate animal. The mountain howitzer is also employed for prairie service, and in defending camps and frontier forts against Indians, in which case it is mounted on a light four- wheel carriage, called " the prairie carriage." In the Mexican war, the mountain howitzer was found useful, from the facility with which it could be carried up steep ascents, and to the tops of flat-roofed houses, in street-lighting. SIEGE AND GAERISON CANNON. Siege cannon are intended for attacking, and gar- rison cannon for defending, inland fortifications and the land fronts of sea-coast fortifications. They comprise guns, hmoitzers, and mortars. 147. Siege g-ims. A siege gun is constructed to throw a solid projectile with the highest practicable velocity, in order to penetrate the masonry of revetments, and to diminish the curvature of the projectile's flight, thereby increasing its chances of hitting objects but slightly raised from the ground. Rifled guns having been found to fulfill these condi- tions more fully than smooth bored guns, they have entirely superseded the latter for siege purposes. A siege gun, properly so called, is one that can be mounted on a siege cairiage which serves both for the purposes of transportation and for firing. Very large guns, as the 10-inch columbiad and 8 and 10-inch lifle- guns were used in the siege operations of the late war. SIEGE MOETAES. l.'?5 hut they are not teclinically siege guns, for no suital)lo carriages have been yet provided for their transportation over common roads. Whenever railroad or water com- munications will permit them to be transported, the largest guns may be employed in siege operations with great effect. The two siege guns now in use are the 4^ inch and the 30-pdr. rifle?. Four and a half in.-rifle-gun. The 4^ inch rifle-gun Is made of cast-iron, cooled from the exterior ; the great length and small size of the bore rendering the water- cooling process impracticable. Its form is similar to that of the 3-inch field-gun (see fig. 41 (£). Weight, Dimensions, c&c. The principal weight and dimensions of this gun are as follows, viz. : Weight, - 3,450 lbs. Diameter of bore. 4.5 in. Length of bore, ■ 261 diam. Number of grooves, - 9 Depth of grooves, - .075 in. Twist of grooves, - - 15 ft. Weight of projectile, - - 30 lbs. W eight of powder, - 3.25 lb. This piece is mounted on the 12-pdr. siege carriage, slightly modified. TJdrty-pdr. rifle-gun. This gun is made of cast-iron reinfoi-ced, after the plan of Captain Parrott, with a band of wroaQ:ht-iron. Its bore is 4.2 inches diameter, and its length about 28 diameters. Its weight is 4,200 lbs., and it is carried on the 18-pdr. siege carriage. The weight of its projectile and charge of powder are the 18(5 CANSrON. SIEGE AND GAREISON CANNON- same as for tlie 4i-inch gun. It has no preponderance, and has been found to be a very accurate and reliable gun in service. 148. Siege howitzer. The suge Jiowitzer, is -princ'i'pal- ly employed for riooohet firing, and for the purpose of battering the earth and fragments of masonry which are left standing after the fire of the breaching guns has ceased. Dimensions^ c&c. The form of this howitzer is shown in fig. 44. Its bore is 8 inches in diameter, and it has an elliptical chamber, and the maximum charge is 4 lbs. of pow- der. As this piece is sometimes fired over Fig. 44. the heads of men in the advanced trenches, no sabot or cartridge-block should be used in it except for canister. The size of the trunnions and the distance between the rimbraces are made the same as in the 24.pdr. gun, that it may fit the 24-pdr. siege carriage, in which case a quoin is used for elevating instead of the ordinary screw. It would be an improvement in the working of this piece were it without preponderance. Its weight is 2,550 lbs. It has the advantage over the old siege how- itzer that the projectile always rests in contact with the powder, however small the charge, and the consequence is that the ranges are greater for the smaller charges. This piece fires mortar shells, spherical-case, grape, and canister shot. By taking off the wheels of the car- riage, and reversing the piece in its trunnions, and sup- porting the whole with strong timbers, this piece may SIEGE MOETAES. 187 le used as a mortar, in which capacity it gives very long ranges. 149. Siege mortars. Siege mortars comprise the com- mon mortars and Coeliorn mortar. The stone mortar was formerly used for siege purposes, but is now laid aside. Dimensions. The form of the common siege mortars is shown in fig, 45. There are two sizes, the 8 and 10 inch, so called from the diameters of their bores. They have no pre- ponderance, and elevation and de- pression are effected by a lever Fig. 45. the point of which acts in a ratchet {a a) cast on the breech. The fulcrum of this lever is attached to the rear transom of the mortar-bed. The chamber is elliptical as in the siege howitzer, and for the reason given in the description of that piece, the new mortars give longer ranges than the old ones. The bores of these mortars are about two diameters long, and the weights about 22 times that of the projectiles, respectively. To prevent the primers from pulling out of the vent, there should be a grooved pulley attached to the devis-hig (b) for the lanyard to pass over. Vertical field of fi/i'e. The vertical field of fire lies between 30° and 60°. The angle at which mortars ai-e usually fired is 45°. This gives very nearly the max- imum j-ange for a given charge of po-\vder. Natural line of sight. The exterior form of the siege mortars is cylindrical; consequently tbe natural line of sight is parallel to the axis of the bore, — a position of great convenience in aiming. The line of sight should l)e permanently marked on the piece while it is in the boring mill. 188 CANNOJSr. — SIEGE AND GARRISON CANNON. Object. Siege mortal's are used to attain tliose poi-- tious of a work, by vei'tical fire, which are defeiideil against the direct and ricochet fires of guns and how- itzers, such as the covered way, the ditch with its com- munications, and the roofs of magazines, casemates, etc. Projectiles. The projectile principally used in moi-- tars is the shell, which for the 8-iiich weighs 44 lbs., and for the 10-inch, 88 lbs. General Bormann, of the Belgian service, some years ago proposed to convert the 10-inch mortar shell into a spherical case shot by filling it with balls about the size of 12-pdr. canister shot, and a bursting charge sufficient to rupture the shell ; the fuse to be timed so that the projectile^would burst about 50 feet from the ground. The effect of such projectiles at the siege of Petersburgh is thus described by General Abbott, the commander of the siege batteries : "Tliis battle was probably the first in which spherical case shot fi'om heavy mortars was used. The expedient of glutting thirty 12-pdr. canister shot under the burst- ing charge of the 10-inch shells was of great utilitj^, their steady fire keeping quiet the most dreaded flank- ing batteries of the enemy's line," From its lightness, and consequent mobility, the 8-inch mortar may be usefully employed in reaching an enemy sheltered by temporary field works. 151. Coehorn mortar. The Coehorn mortar, so called from after its inventor, General Coehorn, is a very small bronze mortar, designed to thi^ow a 24-pdr. shell to dis- tances not exceeding 1,200 yds. Its weight is 164 lbs., its maximum charge | lb. of powder, and it is mounted on a wooden block furnished with handles, so that two SEA-COAST CANNON. 189 men can easily cany it from one part of a work to anothei'. In the late war this piece was much used in the field against troops covered by rifle-pits. At Fort Wagner, General Gillmore says that it followed close on the heels of the sappers and did good service against the enemy who were not sheltered against vertical fire. If fired with friction primers, this mortar should be provided with a shield of sheet-iron so placed as to pre- vent the fragments of the primers from flying among the gunners. SEA-COAST CANNON. 152. Object. Sea-coast cannon ai-e mounted in sea- coast batteries for' the defence of harboi-s, roadsteads, etc., against vessels of war. The efficiency of all cannon depends on their calibre, combined with facility of manoeuvi-e, or rapidity of fire. As sea-coast cannon generally occupy permanent posi- tions, the weight of the piece and projectile is not a serious objection to an increase of calibre, provided the proper mechanical facilities are supplied for moving them with celerity. Projectiles of 10-inch calibre can be handled by two men. Those of 15-inch calibre I'e- quire the aid of machinery to lift them quickly to the muzzle of the piece. 153. tai-gc cannon. It is proposed to mount special cannon of very large calibre at certain points command- ing the entrance to the most important harbors. The intention in such cases is that the projectile shall con- tain powder enough to constitute a mine^ and destroy an 190 CAK-WOX. — -SEA-COAST CANNON. enemy's vessel tlie blow of the hammer from straining the cone, and breaking it off in the cone-seat, the plane of the face of the hammer should pass through the axis of motion. Calibre, Three important points are to be considered m determining the calibre of small-arms: 1st. The calibre should be as small as possible, to enable the soldier to carry the greatest number of cartridges;: with the present calibre, the number of musket-car- tridges is limited to 40 ; the total weight of which is about 2>\ lbs. 2d. To diminish the amount of ammu- nition required to supply the wants of an army, and to prevent the confusion that is liable to arise from a va- riety of calibres, there should not be more than two, for all arms of the same service, viz., one for the musket and one for the pistol. 3d. This point relates to the force and accuracy of the projectile. The introduction of elongated projectiles affords the means of increasing the accuracy and range of fire-arms, without increasing the weight of the projectile, simply by reducing the cal- ibre, which diminishes the surface opposed to the air. : Too great reduction of calibre, however, gives a very long and weak projectile ; and besides, the effect of a projectile on an animate object, depends not only on- its penetration, but on the shock communicated by it to the nervous system, or upon the surface of contact.-. A projectile of very small calibre, having but little iner- tia, does not expand well into the grooves of the bore, ; by the action of the powder ; it is not, therefore, suited to the present method of loading, at the muzzle. The foregoing considerations led to a general reduc-; tion of calibre on the introduction of rifles for military \ 294 SMALL-AEMS. POETABLE FIEE-AEMS. purposes; The present rifle calibre is .58 incli ; that of the pistol (navy size) is .37 inch. Length of larrel. The length of a gun-barrel is de- termined by the nature of the service to which it is applied, rather than by the effect which it exerts on the force of the charge. It has been shown by experi- ment, that the velocity of a projectile, in a smooth- bored musket, increases with the length of the bore, up to 108 calibres, at least ; but a musket with this length; of barrel, would be too heavy as a fire-arm, and too un- wieldy as a pike. The length of the present musket- barrel is TO calibres, or 40 inches. Grooves. 'The principal cause of the deviation of a projectile from its true line of flight is the rotary motion which it receives in the bore of the piece, combined with the resistance of the air. In a smooth-bored bar- rel, variable causes conspire to produce rotation, conse- quently the deviation which results from it, is variable and uncertain. In addition, therefore, to giving a pro- jectile the requisite initial velocity and direction, a gun- barrel should be constructed to give it a certain rotary motion that shall continue throughout its flight. This rotary motion, for reasons stated in discussing rifle-can- non, takes place around an axis coinciding with that of the barrel, and is produced by spiral grooves cut on the surface of the bore. The points tq be observed in constructing rifle-grooves for military arms, are range, accuracy of fire, endurance, and facility of loading and cleaning the bore. For ex- panding projectiles, experiment shows that these points are best attained by making the grooves broad and shal- low, and with a moderate twist. LOCK. 295. The following is a description of the grooves adopted by the United States' government, viz. : Number. Three. Width. Equal to the lands, or one-sixth the circum- ference of the bore. D.epth. Uniformly decreasing from the breech, where it is .015 in., to the muzzle, where it is .005 inch. Twist. Uniform, one turn in six feet for long or musket, and one turn in four feet for short or carbine barrels. The effect of decreasing the depth of rifle-grooves is to increase the accuracy, but diminish the range. The; increase of accuracy, undoubtedly, arises fiom the fact that the projectile is held more firmly by the grooved, us it passes along the bore; while the diminution of range arises from an increase of friction between the projectile and the grooves. The twist is dependent on the length, diameter, and initial velocity of the projectile; in other words, it should be increased in a certain proportion to the length, of the projectile;* and for the same weight of projectile, it should be increased in a certain proportion as thg length of the bore is diminished. Experiment, how- ever, is the surest way of determining the most suitable twist for any projectile. 266. tiock. The lock is the machine by which the charge in the barrel is ignited. Neai-ly all the locks of the present day belong to the percussion class, in which, fire is produced by the blow of a hammer upon a small charge of percussion powder contained in a copper or, paper cap. * See section on iifle-cannon. 296 SMALL-AEMS. POETABLE FIEE-AEMS. The conditions to "be fulfilled in the construction of a military lock, are — • 1st. The production of fire, and its communication with the charge, should be certain, and under the per- fect control of the soldier. 2d. The cap should be placed upon the cone with facility, and it should not be displaced in handling the piece. 3d. Fragments of the cap should not incommode per- sons near by, nor should the gas generated by the explo- sion of the cap corrode or injure the cone, barrel, or stock. 4th. There should be no danger of accidental ex- plosions. Nomenclature. The ordinary percussion lock is com- posed (see fig. 94) of the loch^late (1), to which the several parts are attached, and by which the lock is fastened to the stock; the hammer (2), which strikes upon the cap, and explodes the composition ; the main- ^'s- s*- spring (3), which sets the hammer in motion; the ttum- Uer (4), or axle, by which the power of the main-spring is communicated to the hammer ; the sear (5), or lever, the point of which fits into the notches of the tumbler, and holds the hammer in the required position; the notches are designated as ihe full-cock notc\ and safety- notch' the sear-spring (6), which presses the point of the sear into the tumbler notch ; the hridle (omitted in the figure), which is pierced with two holes for the inner pivots of the sear and tumbler ; the swivel (Y), which joins the main-spring and tumbler. LOCK. 297 Self griming. Tlie foregoing constitute the essential parts of an ordinary percnssion-lock ; in addition to these, the new service lock is supplied with Maynard's self-priming apparatus.* The primer used in this ap- paratus, is a long strip of paper containing about 60 charges of percussion-powder, distributed at uniform intervals. The strip is wound up in the form of a coil, and inserted in a cavity cut into the exterior surface of the lock-plate, called the magazine. One end of the coil protrudes through an opening in the magazine (8), so that the centre of the first charge of percussion- powder is directly over, but not in contact with, the top of the cone. When the lock is sprung, the primer is cut off by a knife-edge on the lower side of the face of the hammer, carried forward and exploded on the top of the cone. K feeding-finger (9), connected with the tumbler, pushes out another primer, when the hammer is brought to the position of " full-cock." Other methods are used for self priming, in some of which the primer is enclosed in the cartridge itself ; but few are found, under all qircumstances, to be as reliable as the common percussion lock. JBack-action. In the back-action lock, the main-spring . is placed in rear of the tumbler, and the sear-spring, as a separate part, is dispensed with. The mortise, which forms a bed for this lock, seriously affects the strength of the stock at the handle ; and, for this reason, the front-action lock is generally preferred for military arms. Accidents. If the head of the hammer be allowed to * In 1861, the self-priming apparatus was omitted in all arms of the V. S. ser- vice, as it was not found to work well in practice. ' 298 SMALL-AEMS. POKTABLE riEE-ABMS. rest on tlie cap, an explosion ■will be liable to follow an accidental blow on the hammer. 267. stock. The stock is the wooden part of a fire- arm, to which all the parts are assembled. Kg. 95. The most important portions of the stock (see fig. 95) are the butt (1), the luindle (2), the liead (3), the grease- box* (4), the beds for the barrel, lock, band-springs, guard- plate, butt-plate; the shoulders for the tip and bands, and the ramrod-groove. The material of the stock should be light and strong. Well-seasoned black walnut is generally used for mili- tary small-arms. The butt is intended to rest against the shoulder, and support the recoil of the piece ; it should be of such length and shape as will enable it to transmit the recoil with the least inconvenience to the soldier. The longer it is, to a certain extent, the mpre firmly will it be press- ed against the shoulder, and the effect of the recoil will be a pusli rather than a blow. The stock is crooked at the handle, for convenience in aiming, and for the pur- pose of diminishing the direct -action of the recoil. Changing the direction of the recoil, in this manner, causes the piece to rotate around the shoulder with an intensity proportional to the lever arm ab ; whence it follows that, if the stock be made too crooked, the butt will be liable to fly up and strike the soldier's face. 268. Sights. The sights are guides by which the piece * Omitted in 1861. SIGHTS. 299 is given the elevation and direction necessary to hit the object. There are two, called front and ream' sights. The front sight is fixed; in the rifle-musket it is formed by sharpening the top of the bayonet-stud, so that its edge shall present a point to the eye of the marksman. The fineness of this point is regulated by the length of the barrel, or distance from the eye, and the size and distance of the objects generally aimed at ; it is made coarser in military than in sporting arms, to prevent injury. The rear sight is composed of a base, which is firmly secured to the bari'el at a short distance from the breech, and a movable part capable of being adjusted for dif- ferent elevations of the barrel. The sight originally afiixed to the rifle-musket had a single leaf, to which was attached a slide, containing the sight notch, which could be adjusted for all distances between 100 and l',000 yards. By a late order of the war department, this has been replaced by a sight which has three mov- able leaves, turning on a common axis, and bearing notches adjusted to 100, 300, and 500 yards, respect- ively. Aiming a fire-arm consists in bringing the top of the front sight, and the bottom of the notch of the rear sight, into the line, joining the eye and the object. A sight for a military arm should satisfy the following conditions, viz. : 1st. It should be easily adjusted for all distances within effective range; 2d. The form of the notch should permit the eye to catch the object quickly ; od. It should not be easily deranged by the accidents of the service. The globe and telescopic sights are used for very accu- 300 SMALL-AEMS. ^POKTATJLE FIKE-AEMS. rate sporting-arms, but they are too delicate in their structure, and too slow in their operation, for general purposes. In the absence of a proper rear sight, the soldier of the line may be taught to point his piece by aiming over the centre of the knuckle of his left thumb ; the position of the thumb along the barrel determines the elevation of the piece. This method is practised by certain French troops of the line, for distances less than 400 yards. 269. Mountings. The mountings comprise the hitt- ^late, the guard-plate, the hands, springs, and tip. The hutt-plate protects the end of the stock from in- jury by contact with the ground ; it is curved to fit the shoulder in firing, and is secured in its place by two wood-screws. The guardplate strengthens the handle of the stock, and serves as a fulcrum for the trigger. It is secured by the tang-screw and two wood-screws. The trigger is a lever used to disengage the point of the sear from the notch of the tumbler, which sets the lock in motion. The force required to set off the trig- ger, if very great, niay disturb the accuracy of the aim ; if it be slight, the piece will be liable to accidental discharges, as in the case of the hair-trigger used in target-pieces. The guard-how protects the finger-piece of the trigger from injury, and from accidental blows that might pro- duce explosions. The hatids secure the barrel to the stock, and the springs keep the bands in their places. If the piece be intended to be carried upon the soldier's back, it is pro- BREECH-LOADING AEMS. 301 vided with two swwels, one of which is fastened to the guard-bow, and the other to a band. 270. Ramrod. The ramrod is the long, slender piece employed in muzzle-loading arms, to push the charge to its proper place, and to wipe out the barrel. It is carried in a groove cut into the under side of the stock, and it is kept in its place by the pressure of the swell against the tip of the stock. The head of the rod is countersunk to fit the point of the projectile ; and the point has a screw to receive the wiper and halUscreio — implements that are used to clean and remove obstruc- tions fi'om the bore. BREECH-LOADING ARMS. 271. General description. The term " bi'eech-load- ing" applies to those arms in which the chai-ge is in- serted into the bore through an opening in the breech; and, as far as loading is concerned, the ramrod is dis- pensed with. The interior of the barrel of a breech-loading arm is divided into two distinct parts, viz., the hore proper, or space through which the projectile moves under the influence of the powder; and the cliamher in which the charge is deposited. The diameter of the chamber is usually made a little larger, and that of the bore a little smaller, than that of the projectile ; this arrangement facilitates the insertion of the charge, and causes the projectile to be compressed, and held firmly by the lands ill its passage through the bore. As before stated, this operation is called slugging the projectile. The bottom of the grooves and the surface of the chamber are generally continuous. 302 SMALL- ARMS. — BEEECH-LOADING. If tlie chambei" be made in the piece which closes the breech, commonly called the hreecli-hlock, the aim is said to have a rnovable chamber; if it be formed by counter- boring the barrel, it is said to be sl fixed chamber. The fixed chamber has great advantages, and is now gen- erally used, especially for the metallic case cartridge. Formerly the most serious defect of breech-loading arms was the escape of the flame through the joint, .which not only incommoded the soldier, but by fouling the machinerj', seriously interfered with its operation. At present this is entirely overcome by "packing the joint" vs'ith a thin steel ring, which is a part of the gun and called the "gas-check," or by the case of the car- tridge itself. The elasticity of the case, if made of cop- per or brass, is such that it may be used repeatedly if any provision is made for re-priming it with fulminate, as in sporting guns. Systems. At the present time breech-loading arms may be divided into old and new systems. The old system is characterized by the use of the percussion-cap ; the new system by the self-primed metallic case car- tridge. About the only breech-loading arms of the old system now found in our service are Sharp's. 272. Sharp's fire-arms. In Sharp's fire-arms the chamber is fixed (see fig. 96) and the barrel closed by a sliding breech-piece (a), which moves nearly at right angles to the axis of the piece. Formerly there was no attempt to prevent the escape of gas through the joint, or opening between Fig. 96. SELF-PEIMED 3IETALLIC CASE OAETBIDGES. 303* the slide and barrel, and after a few discharges in dry- weather the movement of the slide became clogged with burnt powder. By boring a recess into the face of the slide, opposite to the chamber, and inserting a tightly-fitting steel ring (b b) into it, in such a manner that the inner rim is pressed against the end of the bar- rel by the force of the powder, the escape of gas is pre- vented. This fire-arm is loaded by depressing the lever, or trigger-guard, which withdraws the slide and opens the breech for the insertion of the cartridge. The car- tridge is composed of a linen cloth cylinder to contain the powder, one end of which overlaps and is gummed to the base of the bullet ; the other is closed with a layer of thin bank-note paper. The flame of the percus- sion-cap penetrates through this paper and ignites the powdei'. The linen case is carried out with the bullet, and drops to the ground a short distance in front of the piece. 273. Metallic cartrids^e. One of the most marked improvements in small-arms, developed by the late war in this country, is the use of the self-primed metallic case cartridge for breech-loading arms. This cartridge (fig. 97) is composed of a thin copper case (a), with a projecting rim (&). The case is formed by cutting a circular disk out of a sheet of ISTo. 22 (wire gauge) cop- per, and punching it into the shape of a cup, or short cylinder closed at one end. To give this cup the proper length, its sides are drawn out by forcing it in suc- cession, with punches, through four sets of ^B-^f- (jies^ each operation making the sides longer and thinnei- than the preceding. 303 SMALL-AKMS. ^BREECH-LOADING. Ill these drawing operations the cages are moisi.ened with soap-suds, and the copper is annealed one or more times (depending on its quality), to prevent cracking. The open end is trimmed in a lathe ; and the metal at the head is crowded up so as to overlap the sides and form a projecting rim. This rim furnishes a hold for the ex- tractor, which withdraws the empty case from the gun after firing. In some cartridges the fulminate is placed in this rim, and it is exploded by the firing-pin pressing the rim against the counterbore of the barrel ; these are known as side Jh^e cartridges. In fhe cartridge lately adopted for the altered Springfield rifle-musket, the ful minate is placed in the cavity of an iron bar, or a7ivil (c), and in contact with the centre of the head of the case, as shown at {d) in the figure. The anvil, which has to sustain the blow of the hammer communicated through the firing-pin, is held in place by crimping the sides of the case into the groove at each end. To prevent cor- rosion, the anvil is tinned. The case is tajDered from the head to the open end .02 inch at the same time that it is crimped; this taper facilitates the withdrawal of the case from the chamber of the gun. The lubricant, which is composed of two parts of parafine and one of hayherry tallow, is protected in the grooves of the bullet by the overlapping of the case, as shown in the figure. The figure I'epresents the parts of the cartridge of the natural size. The bullet is solid and weighs 450 grs., and the powder TO grs. Advantages. The advantages of this kind of car- tridge are : — 1st. It is self-primed, and the operation of loading is simplified ; 2d. The case is strong and not easily disfigured, and the powder and priming within . BEEEOH-LOADING RIFLE-MTJSKETS. 303* it are protected from injury ; 3d. The certainty of put- ting the proper amount of powder into the piece in loading ; 4th. The axis of the bullet is made coincident with that of the bore when the piece is loaded, and an important cause of inaccuracy of fire is obviated: 5th. The cartridge case is a perfect gas-check, which prevents the machinery of the gun from being fouled and worn by the flame of the powder. When the loss by wear and tear of the oi'dinary car- tridge is taken into consideration, it is thought that it is little, if any, cheaper than those with metallic cases. Ex- perience shows that the latter can be handled and trans- ported with safety, and that the explosion of one or more will not extend to others in the same box. Such cartridges have been kept under water more than two months without injury; a portion of the time the water was frozen. 274. Principles of breech-loading: arms. Breech- loading arms of the new system may be divided into 6'imple breech-loaders and repeaters. The principal paijts peculiar to the former are : 1st. The movable hreeGh-hlock^ by which the cha.mber is opened and closed ; 2d. The hreecJi frame upon which the breech-block is mounted and united to the barrel ; 3d. The cliamher.^ with its counterbored recess, to receive the rim of the cartridge; 4th. The firing-pin, which transmits 'the blow of the hammer to the priming of the cartridge ; 5th. The ex- tractor, by which the empty case is removed after firing. In addition to these parts, the repeater has a maga- zine attached to it to contain a certain number of car- tridges, which are successively brought into the chamber by peculiar mechanism. 304 BREECn-LOADING ARMS. The foregoing named parts may be said to be essen- tial to all bi-eecli-loading arms in which the metallic cartridge is used ; the different ways in which they are combined mark the different systems now in vogue. These combinations have reference chiefly to the modes of operating and locking the breech-block. The breech- block may be operated in two ways : 1st, by rotation^ where it swings on a hinge; 2d, hj sliding^ where it moves in grooves. The former mode is generally to be preferred, as the rubbing surfaces are small, and the power is applied at the end of a lever; in the same way that it is easier to close a hinged door than a slidintr oue. In the rotating breech-block, the position of the hinge has an important influence on the facility of operating the block, inserting the cartridge and withdrawing the empty shell, and the most suitable position is deemed to be in front of the centre of the block. In this case the motion of opening and closing the block is natural and easy, the cartridge is pushed into its place by the bl(?ck, and a very simple retractor serves to withdraw the empty shell after firing. The Allin (Springfield altered), Berdan, Millbank, Lamson, Remington, Laidley, and others belong to this class. In the last two named the hinge is below, in the others it is above the axis of the block. In the Snider (Enfield altered), Warner, Maynard and others the hinge is on the side of the block ; while in the Peabodj', Roberts and others it is in ]-ear. In the Prussian-Needle, the French Chassepot, Root, Meigs, Sharp and other guns the breech-block is made to slide. There is another system, however, in which the breech is opened by moving the barrel. This system is better adapted to sporting than to military guns. SJIALL-ARjrS. BREECn-LOADlNG. 304'' The following are among the more important con- ditions to be fulfilled in constructing a breech-loading gun of the new system, viz. : 1st. The strength and union of the parts should be such as not, only to I'esist repeated discharges, but the bursting of a car- tridge case, which sometimes occurs from defective ma- terial or workmanship. 2d. The locking of the breech- block should not only be secui-e, but all the parts by which it is effected should woik freely — without stick- ing. 3d. The parts should be so arranged that the hammer cannot strike the firing-pin until the breech- block is properly locked. 4th. The piece should not be carried loaded with the hammer restinsTt on the fii'ing:- pin. 5th. Avoid, if possible, the necessity of bringing the hammer to the full cock in order to unlock the breech-block. Oth. The working parts should, as far as possible, be covered from dust and water. Tth. The extractor should be so arranged as to requii'e no cuts or openings in that part of the chamber which sur- rounds the body of the cartridge case. 275. Altered Stn-ing-field musket. There being a large number of serviceable Springfield rifle-muskets on hand, the War Department has decided to I'educe the calibre of a portion of them and change them into breech-loaders for issue to the army. By these alterations, the i-ange, accuracy and rapidity of fire are increased, and the weight of the ammunition diminished. Reduction of calibre. The bore is~ reduced from its original size — .58 inch — to its present size — .50 inch — by reaming out the grooves and inserting a tube of wroughf- iron. To give a proper bearing to the tube, the bore and exterior of the tube are slightly tapered fi'om the 305 BREECH-LOADINa EIFLE-JTUSKETfl. hreech to tlie muzzle. The tube is then introduced through tlie breech of the barrel, and driven with a hammer until the two are in close contact throughout. Both ends are then made solid by brazing under a blow-pipe, after which the barrel is re-proved, finish- boi'ed, and rifled with three broad grooves with a twist of 42 inches, and a depth of .0075 inch. BreeeJi-loadivg alteration. In general terms, the breech- loading alteration is made by cutting an opening into the top of the bari'el for about 3 inches from the breech- screw, and inserting into this opening a breech-block, which is hinged at its for- ward end to the barrel. Its rear end is locked by a cam, which fits into a circular re- cess cut in the end of the breech-pin. Fig. 98 repre- sents a vei'tical section of the musket tlius altered. {a) is a portion of the barrel around the cliamher ; (h) is the hreech-hlock ; {c) the liinge-strap to which this block is attaciied ; (r/) is the Pi gg breech-pin with its circvlar recess ; (e) is the cam-latch wliich fits into this recess, thus lockinij the breech-block in place ; (/) is a cam-latch spring, to press the cam-latch SJIALL-AKMS. BKEECH-LOADINO. 305* into the recess; {g) is the firing-pin which transmits the blow of the hammer to the priming of the cartridge; (i) is t\\e firing-pin spring, to press the pin back when the hammer is raised ; (_;') is a projection on the breech-block,, called the extractor hooTc, to loosen the empty cartridge- case when the breech-block is thrown forward into the position of loading shown in the broken lines of the figure; (o) is the ejector spring, one end of which is fastened to the barrel and the other projects through the barrel and presses on the inner portion of the rim to eject the case from the gun; (0 is th.Q friction spring, the point of which presses against the rim of the case and. holds it against the effort of the ejector spring, until the hook starts it; this will not take place until the chamber has been uncovered by the breech-block ; {n) is the ejector stud against which the case strikes and is deflected from the piece ; (m) is the screw which fastens the ejector spring to the barrel; {pp) are screws which attach the hinge-strap to the barrel, and Qc)^ is the pivot screw about which the breech-block turns. The cam-latch is raised and lowered by a thumb-piece attached to the cam-latch shaft which projects through the old cone-seat of the barrel. To the thumb-piece is attached a branch which covers the head of the firing- pin, and. prevents an accidental discharge of the gun until the cam-latch is in place, and the breech-block is locked. 276. Spencer repeatingr arms. The magazine of the Spencer repeating fire-arm lies in the butt of the stock — fig. 98 (,«) — and is capable of holding seven copper case cartridges. Weight of powder 45 grs.,bullet 350 grs. A follower (a) impelled by a spiral spring pushes the 306 SrENCER EEPEATING ARMS. line of cartridges towards the chamber of the barrel. When the chamber is closed, tlie point of the foremost Fig. 98 {a). cartridge rests against the carrier-Mock (F). When it is opened, which is done by depressing the lever guard (c), this cartridge is pushed forward into the position shown ia the figure. By raising the lever guard the cartridge is carried around and pushed into the mouth of the chamber, w^hich is firmly closed by the hreech- hloch {d). The extractor (e) is a flat lever attached to the left side of the carrier-block, and withdraws the empty case by pressing against the under side of the rim. Another small lever, called the guide (/), falls into the space occupied by the carrier-block, and forms an inclined plane, up which the empty case moves to clear the piece. A Jsei/ (not shown in the figure) has lately been introduced into this arm, by which the supply of cartridges can be cut off or let on at pleasure, and enables the soldier to reserve the cartridges in the magazine for an emergency. When the magazine is SjMAll'Aum projectiles. 307 locked, the piece can be loaded directly from tlie car- tridge-box, as a simple breech-loader. The operation of this key is simply to prevent the carrier-block from fall- ing so far as to uncover the magazine, at the same time it falls far enough to uncover the chamber for^ the in- sertion of a cartridge by hand. Other ingenious repeating arms have been devised, but none have been so generally used and approved as the Spencer arm. 277. Advantages, *c. The advantages of breeeh- loading over muzzle-loading arms are : 1st. Greater cer- tainty and rapidity of fire ; 2d. Greater security from accidents in loading ; 3d. The impossibility of getting more than one cartridge into the piece at the same time ; 4th. Greater facility of loading under all circumstances^ and particularly when the soldier is mounted, or lying upon the ground, or firing from behind a cover ; 6th. The greater security with which the charge is kept in place when the piece is carried on horseback with' the muzzle down. The results of the late wars in this country and Germany have led to the introduction of breech-loading small-arms for all branches of military service. SMALI^AEM PROJECTILES. 278. Forcing. " Forcing," as applied to a projectile, is the operation by which it is made to take hold of the grooves of a rifled barrel, and follow them in its passage through the bore. It may be accomplished in various ways^ most of which, depend upon the soft and yielding ■'308 SMALL-ARMS. PKOJECTILES. nature of lead, tlie material of which, small-arm projec- tiles are made, viz. : 1st, By" the action of the ramrod. 2d. By the action of the powder. 3d. By the action of ramrod and powder combined. 4th. By the form of the bore or projectile, as in breech-loading arms, &c. 279. By the action of tlie ramrod. When rifles Were first made, forcing was effected by making the projectile a little larger than the bore, and driving it down with a mallet applied to the point of the ramrod; although 'this caused the lead to fill the grooves completely, con- verting the projectile into a screw, whereof the barrel was the nut ; the operation was slow and laborious, and the accuracy of the projectile was impaired by the consequent Kg. 99. disfiguration. The form of the grooves then used is shown in fig. 99. They were liable to be injured by the ramrod, and were difficult to clean. 280. Patch. The foregoing plan was improved by making a projectile a little smaller than the bore, and wrapping it with a patch of cloth, greased, to diminish friction in loading. The thickness of the cloth was greater than the windage; this caused the patch to press upon the projectile with so much force as to com- pel it to follow the winding of the grooves without ma- terially altering its shape. The patch is still used in sporting rifles, and gives excellent results ; but the load- ing is too slow and difficult for a military arm. ■ 281. ©elvigiie's plan. M. Delvigne, an officer of the French infantry, appears to have been the first person TIGE, OR 8PIKDLE. 309' wlio overcanie the difficulty of loading rifleSjtliereby re- moving the principal obstacle to their introduction into the military service. The plan proposed by him, in ISST, was to make the projectile small enough to enter; the bore easily, and to attach it to a sabot^ or block of ; wood (a, fig. loo), which, when ■ in position, rested upon the the shoulders of a cylindrical chamber (5), formed at the bot- Fig. 100. ^Qjjj q£ jq^^ "bore, to contain the ; powder. In this position, the projectile was struck two ■ or three times with the ramrod, which expanded the lead into the grooves of the barrel. To the bottom of the sabot was attached a piece of greased serge, which J' served to soften the residuum of the powder and facili-? tate the loading. By this plan the accuracy of the round projectile was increased, but its range was di- minished. Elongated projectile. In 1742, Robins pointed out the superiority of the oval, or elongated form of projec- tile, and since this many attempts have been made to employ it in rifled arms, especially in this country, but^ it remained for M. Delvigne, followed by MM. Thouve- nin and Mini^, of the French service, to apply it sue-' cessfully to the military service. The form of projectile proposed by these officers was i composed of a cylinder and conoid. The cylinder served as the base of the projectile, and gave it stability in the bore of the piece; the conoidal surface, which formed the point, was well adapted to diminish thC; effect of the air, by increasing the penetrating power of the projectile. A single groove was formed around the'' 310 SMALL- ARMS. PROJECTILES. cylinder, to contain a greased woollen thread, in place of the woollen patch of Delvigne. It was shown by the trials which followed, that the presence of this groove improved the accuracy of the projectile — a fact which gave a new turn to the inves- tigations, and led to the adoption of two additional grooves. The theory advanced in explanation of the aiction of these grooves was, that they oppose a resist- ance to the air, which, acting on the rear portion of the projectile, tends to keep the point foremost in flight, thereby rendering the resistancp of the air uniform, and at the same time a minimum. , The correctness of this theory may he well questioned; but that the grooves exert a beneficial effect, by dimin- ishing adhesion to the surface of the bore, and by facili- tating expansion, can scarcely admit of a doubt. ; 282. Tige, or spindle. Colonel Thouvenin proposed to replace the chamber of Delvigne by a spindle of iron, screwed into the centre of the breech-screw (see a, fig. 101). This was found to be an excellent point of support for the base of the elongated bullet when forced by the blows ^'^•i"^- of the ramrod. The ex- pansion of the lead into the grooves secured the bullet in place, and protected the powder from moisture. Considerable difficulty, however, was experienced in deaning the space around the spindle; and, like all plans of forcing by the ramrod, it is subject to variation, arising from the particular care and strength exercised by the soldier. BY THE POWDEK. 311 283. By form of projectile. This method of forcing is illustrated in the Whitworth. rifle. The form of the l)ore, as in the cannon, is a twisted hexagonal prism, making a complete turn in 20 inches. The projectile (fig. 102) is made nearly of the exact form and size of the bore, and is about three diameters in length. To prevent disfiguration and strip- ping^'^' which are very liable to occur in bul- lets of this length, fired with high velocities, the lead is hardened by alloying it with tin and manganese; and to obviate fouling, a '^' ■ greased wad is placed between the powder and bullet. As might be expected from the length of the bullet, the amount of twist, and the extreme ac- curacy with which the bullet fits the bore, the results obtained with this arm are much superior to those ob- tained with service-arms. 284. By the powder. It appears that the first attempt to force a projectile by the action of the powder was made by Mr. Greener, an English gunsmith, in 1836. The plan which he tried consisted in forming a cavity at the base of an oblong bullet, and partially inserting in it a conical pewter wedge, which was driven in by the force of the powder in such manner as to expand the outer part of the bullet into the grooves of the barrel. Some years after this. Colonel Minie pro- duced a projectile constructed on the same principle, but instead of a solid wedge, he used a cup of sheet iron, which was inserted Kg. 103. into a conical cavity (fig. 103) at the base * stripping is the tearing away of the metal when the projectile passes out of the bore without following the grooves. 312 SMALL- AEMS. PEO JECTILES. of the bullet. The point of the ball was cut off to prevent disfiguration by the flat head of the ramrod. This projectile, when fired from a rifle of service calibre, generally possessed great range and accuracy ; but it had certain defects which prevented it from being exten- sively used in military service, viz. : it was compound in its structure ; the cup was sometimes forced in obliquely, producing unequal expansion; and, from the large size of the cavity, the top was occasionally blown off, leaving the cylindrical portion adhering to the sides of the bore. 285. JPresent methods. Not long after the introduc- tion of the .Minie bullet, it was discovered that, by giv- ing a suitable size and shape to the cavity, the wedge could be dispensed with. The projectile thus obtained was simple in its structure, and gave better and more reliable results than the one from which it was derived. The particular form and mode of expanding bullets, varies in most military services ; in general terms, hoAv- ever, all modern small-arm projectiles are cylindro-con- oidal in shape, and a majority of them are forced by the action of the powder. The effect of the powder may be direct, as in the case where it acts in the cavity of a bullet; or it may be indirect, as when it compresses the bullet lengthwise, or, technically, '■'■ttpsets'''' it. 286. United states. The bullet used in the United States service, is derived from that of the carabine a tige, chiefly, by making a conical cavity in its base. (See fig. 104.) The shape of the first cavity employed, was that of a frustum of ^ a cone ; but this was found defective S when used in the rifle-musket, inas- Fig. 104 ENGLAND, FRANCE, AUSTEIA. 313 mucli as it rendered tte bullet too weak at tlie juncture of the two exterior surfaces. For arms with reduced charges of powder, as in the carbine and pistol, the large cavity is most suitable. A description of the musket-bullet has been given in chapter II. A distinguishing feature of this bullet is, that no patch of any kind is used in loading ; in nearly all other modern bullets a greased patch of cloth, or paper, envelops them when placed in the bore, 287. Engiasid. The British bullet (sometimes known as the Pritchett bullet) has a perfectly smooth exterior, (fig. 105.) A conical plug of box- wood is inserted into the opening of the cavity, it is said, more for the purpose of preserving the form of the bullet in transportation than aiding in the expansion. The diameter and weight of this bullet are nearly the same as in the United States bullet. Fig. 105. 288. France. Two distinct bullets are employed in the French army. The first is shown in fig. 101 ; it is heavy, and is intended to have great force and accuracy at long distances. It is used by troops armed with the carabine a tige, as the Chas- seurs and Zouaves. The second bullet is shown in fig. 106 ; it is light, and without much accuracy, describes a flattened trajec- tory, which increases the chances of hitting a line of men at the usual fighting distance. Fig. iog. This bullet is used by troops of the line, who are not supposed to be skilful marksmen. 289. Austria. The Austrian bullet belongs to the class of solid expanding projectiles. In this particular 314 SMALL-AEMS. CHARGE OF POWDER. case, expansion is effected by the crowding up of tlie disks, formed by cutting two deep grooves around the cylinder. (Fig. lOY.) A portion of the Austrian rifles (those carried by the non-commissioned officers, and men of the third rank, who act as skirmishers) have a spindle attached to the breech-screw ; the ob- ject of Avhich is, not to aid in expanding the '^' ^° bullet, but to give it an invariable position with reference to the powder, and thereby secure uniformity of action. 290. Switzerland. Fig. 108 shows the form of the bullet used in the Swiss service. It is solid, and is forced by a cloth patch tied around the grooves. The position of the bullet with refer- ence to the powder is constant ; this is deter- mined by a notch on the ramrod — ^the notch being so arranged as to leave an interval between Fig. los. the powder and the bullet. The diameter of this bullet is much less than that of any other service; and, in consequence of its lightness, it is fired with a larger proportional charge of powder. Within the usual range of small arms, it is said to have a flatter trajectory, and greater accuracy, than any other small-arm projectile ; but at extreme ranges it loses its velocity very rapidly. CHARGE OF POWDER. 291. CoMditions. The proper charge of powder, for a small-arm, depends on the calibre, windage, length of barrel, weight of the piece, and character of the projec- tile. The charge of the old smooth-bored musket was QITALITIES. 315 uot far from one-third the weight of the projectile ; this was necessary to make up for the loss of force by great windage, and to give the round bullet the neces- sary momentum. When the elongated bullet was in- troduced, it became necessary to reduce the charge to prevent too severe recoil ; besides, the mass of the bullet being increased, a diminished velocity sufficed to pro- duce the same effect. In the case of expanding bullets, too small a charge will be insufficient to force the lead into the grooves of the barrel ; at the same time, it is shown by experience that, if the charge be increased beyond a certain point, the bullet is liable to be disfigured by upsetting, and its accuracy is diminished. The proper change for elongated expanding bullets vari-es from one-tenth to one-seventh the weight of the projectile. LUBRICANT. 292. Necessity. After a fire-arm has teen discharged several times, the residuum of the burnt powder collects on the surface of the bore, forming a hard substance which seriously obstructs loading; and unless the nvindage be very great, it becomes necessary to wipe out the bore, or apply some lubricating substance to the projectile. - 293. plaster, forming a tube (c) enclosed in and supported Kg. 126. PEECUSSION-FUZE. 365 by the composition. The composition is ignited in the usual way, at the top, and, as it bums away, leaves a portion of the plaster tube unsupported ; when the shell strikes its object, the shock breaks off the unsupported part of the tube, and the flame of the composition im- mediately communicates with the bursting-charge ; if the tube do not break, the composition burns up, and the bursting-charge is ignited, as in an ordinary time-fuze. The upper portion of the composition burns away quick- ly, in order to leave the tube unsupported soon after the projectile leaves its piece. 375. Percu§sioii-fiise. A percussion-fuse explodes by the striking of some particular point of a projectile against an object, as in the case of rifle-cannon projectiles. One of the best and simplest forms of this kind of fuze is the ordinary percussion-cajD placed on a cone affixed to the point of the projectile. The piece to which the cone is attached may be fixed or movable ; in either case, the apparatus should be covered with a safety-cap to prevent the percussion-cap from taking fire by the discharge of the piece. Fig. 127 represents a fuze of the per- cussion kind, in which 5 is a movable cone-piece, bearing a musket-cap (c) ; and a is the safety-cap which covers the fuze- hole. When the projectile is set in mo- tion, the cone-piece, or " plunger," by its inertia, presses against the shoulders of Kg, 12'r. ^-j^Q fuze-hole;* when its motion is ar- * Late experience stows that the plunger sliould be enclosed in a tight metal case to prevent it from heing fouled by the action of the powder ; and to prevent piematurj explosions, the cone-piec3 should be confined by a screw or other device, to prevent it from moving until the projectile strikes its object. 366 PYEOTECHNY. FIREWORKS FOR SIGNALS. rested, the inertia of the cone-piece causes tlie percus- sion-cap to impinge against the safety-cap, Avhich pro- duces explosion. The explosion of the projectile may be made to take place at any desired time, after the ex- plosion of the cap, by interposing grain, or mealed pow- der, between the cap and bursting-charge. FIREWORKS FOR SIGNALS. The preparations employed for signals are rocJcets and Jjlue-liglits. 376. Signal rockets. The principal parts of a signal rocket are the case (a), the composition (S), the j)ot (c), the decorations (e), and the stick (/). Fig. 128. Case. The case is made by rolling stout paper covered on one side with j)aste, around a former, and at the same time applying a pressure until all the layers adhere to each other. The vent is formed by choking one end of the case, and wrapping it with twine. When the case is trimmed and dried, it is ready for driving the composition. Composition. A variety of compositions are employed for signal rockets ; the best can only be determined l>y trial, as it varies Avith the condition of the ingredients. The following proportions are used at the West Point laboratory : SIGKAL KOCKETS. 367 NITRE. SULPHUR. CHAKCOAL. 12 2 3 to increase the lengtli and brilliancy of the trail, add steel, or cast-iron filings. Driving. The case is placed in a copper mould which has a conical spindle attached to the centre of its base, to form the bore ; the composition is driven with twenty- one Uows of the mallet. The first and second drifts are made hollow to fit over the spindle, and the third is solid. The top of the case is closed by moist plaster of Paris, which is one diameter thick, and perforated with a hole for the jaassage of the flame from the burning composition to the pot. The rocket is primed by insert- ing a strand of quick-match into the bore, after which it is coiled up, and covered with a paper cap, until re- quired for use. Pot. The pot is formed of a paper cylinder slipped over, and pasted to the to]3 of the case ; it is surmounted Avith a paper cone, filled with tow. The object of the pot is to contain the decorations which are scattered through the air by the explosion -which takes place when the rocket reaches the summit of its trajectory ; the explosion is produced by a small charge of mealed powder. Decorations. The decorations of rockets are stars^ serpents, Tnarrons^ gold rain, rain of fire, &c. Stars. Stars are formed by driving the composition, moistened with alcohol and gum-arabic in solution, in 568 PYEOTECHNY. FIEE-WORKS FOE SIGNALS. port-fire moulds. It is then cut into lengths about ^ in., and dredged with mealed powder. White. 1 NITEE. SFLPHUE. MEALED POWDEE. 7 3 2 Jied. CHLORATE OF POTASSA. SULPHUR. LAMPBLACK. ■ NITRATE OF STROk-TIA. 7 4 1 1^ JBlioe. CHLORATE OF POTASSA. SULPHUR. ! AMMONIACAL SULPHATE OF COPPER. 3 1 1 Yellow. CHLORATE OF POTASSA. SULPHUR. . SULPHATE OF STRONTIA. BICARBONATE OF SODA. 4 2 1 1 Serpents. The case of a serpent is similar to that of a rocket, but the interior diameter is only 0.4 inch. The composition is driven in, and the top is closed with moist plaster of Paris. It is primed by inserting a small BLTTE-LIGIIT. 369 piece of quick-matcli through the vent ; it may be inade to explode by driving mealed powder over the composi- tion. The composition is — NITRE. SULPHUR. MBALED POWDER. CHARCOAL. 3 3 16 i Marrons. Marrons are small paper shells, or cubes, filled with grained powder, and primed Avith a short piece of quick-match, which is inserted in a hole punc- tured in one of the corners. To increase the resistance of the shell, it is wrapped with twine, and dipped in hit composition. Stick. The stick is a tapering piece of pine, about nine times the length of the case, and is tied to the side of the case to guide the rocket in its flight. The posi- tion of the centre of gravity depends on the diameter of the case ; for a 2-in. rocket it should be 2-|- in. in rear of the vent; and it is verified by balancing on a knife- edge. The prescribed dimensions of the stick should be observed, for, if the stick be too heavy, the rocket will not rise to a proper height ; if it be too light, it will not rise vertically. 37V. Biue-iigiit. A very brilliant bluish light may be made of the following ingredients, viz. : NITKB. SULPHUR. EK ALGAE. I MEALED POWDEE. .14 3.7 1 1 The brilliancy depends on the purity and thorough 24 810 PTEOTECHBTT. INCENDIAKY EIEEWQEKS. incorporation of the ingredients. The composition may be driven in a paper case, and afterward cut oif to suit the required time of burning. Both ends of the case are closed with paper caps, and primed with quick-match, in order that one or both ends may be lighted at pleas- ure. A light in which the composition is 1.5 inches diameter can be easily distinguished at the distance of 15 miles. INCENDIAEY FIEEWOEKS. . . Incendiary preparations are fire-stone^ carcasses, incen- diary-matcJi, and hot shot. 378. Fire-stone. Fire-stone is a composition that burns slowly, but intensely; it is placed in a shell, along with the bursting-charge, for the purpose of set- ting fire to ships, buildings, &c. Composition. It is composed of — NITKE. SULPHUE. ANTIMONY. - 1 EOSIN. 10 4 1 3 1 Preparation. In a furnace of the second kind, or in a kettle in the open air, melt together one part of mut- ton tallow and one part oi turpentine ; the composition, having been properly pulverized and mixed, is added to the melted tallow and turpentine, in small quantities. Each portion of the composition should be well stirred with long wooden spatxilas to prevent it from taking fire, and each portion should be melted before another is added. CAECA8S. 371 How used. When fire-stone is to be used in shells, it is cast into cylindrical moulds, made by rolling rocket-paper around a former, and securing it with glue. A small hole is formed in the composition by placing a paper tube in the centre of each mould (a, fig. 129). When the melted composition has become hard, this hole is Fig. 129. filled with a priming of fuze composition, driven as in the case of a fuze. The object of this priming is to insure the ignition of the fire-stone by the flame of the bursting charge. There are two sizes of moulds, the largest for shells above the 8-in., and the other for the 8-in. and all below it. 379. Carcass. A carcass is a hollow cast-iron projec- tile filled Avith burning composition, the flame of which issues through four fuze-holes, to set fire to combustible objects. Composition. The composition is the same as for port- fires, mixed with a small quantity of finely-chopped tovj, and as much white turpentine and spirits of turpentine as will give it a compressible consistency; Prepa/ration. The composition is compactly pressed into the carcass with a drift, so as to fill it entirely. Sticks of wood 0.5 in. diameter are then inserted into each fnze-hole, with^ the points touching at the centre, so that when withdrawn corresponding holes shall re- main in the composition. In each hole, thus formed, three strands of quick-match are inserted, and held in place by dry port-fire composition, which is pressed around them. About three inches of the quick-match hangs out when the carcass is inserted in the piece ; pre? 372 PYEOTECHNY. FlEEWOEKS FOE LIGHT. viously to that, it is coiled up in the fuze-hole, and closed with a patch of cloth dipped in melted kit. A common shell may be loaded as a carcass by placing the bursting-charge on the bottom of the cavity, and covering it with carcass composition, driven in until the shell is nearly fall, and then inserting four or five strands of quick-match, secured by driving more composition. This projectile, after burning as a carcass, explodes as a shell. ' 380. imcemdiary inatcii. Incendiary match is made by boiling slow-match in a saturated solution of nitre ; drying it ; cutting it into pieces, and plunging it into melted fire-stone. It is principally used in loaded shells. 381. Hot siiot. For the purpose of setting fire to wooden vessels, buildings, &c., solid shot are heated in a furnace, before firing, to a red heat.* The time required to heat a 42-pdr. shot to a red heat is about half an liour. The precautions to be observed in loading hot shot are, that the cartridge be perfectly tight, so that the powder shall not scatter along the bore, and that a wad of pure clay, or hay, soaked in water, be interposed be- tween the cartridge and the shot. When properly loaded, the shot may be allowed to cool without igniting the charge. ^ FIREWOKKS FOR LIGHT. The preparations for producing light are fire-balls, light-halls, tarred links, pitched fascines, and torches. * In tlio British sea-coast service shells are used for incendiary purposes by fill- ing them with molten iron drawn from a small cupola furnace. If the shell be broken on striking, the hot iron is scattered about ; if it be not broken, the heat pene- trates tliroiigh the shell with sufficient intensity to set wood on fire. nilE-BALL. 373 382. Fire-ball. A fire-ball is an oval-shaped canvas sack, filled with. comlDustible composition (fig. 180). It is intended to be tlirown from a moi'tar to liglit up the Avorks of an enemy, and is loaded with a shell to prevent it from being approached and ex- tinguished. Saclc. The sack is made of sail-cloth, cut into three oval pieces or gores, and ^^s- i^o- sewed together at their edges. Several thicknesses of cloth may be used, if necessary. One end of the sack is left open, and, after being sewed, it is turned to bring the seam on the inside. Composition. The composition for a fire-ball consists of— JSlTiiE. SULPHUR. ANTIMONY. 8 2 1 After being pulverized, mixed, and sifted, the compo- sition is moistened, with one-thirtieth of its weight of water, and again passed through a coarse sieve. The ball is filled by j)ouring a layer of composition into the • sack, and placing the shell (fuze down) upon it ; after this, the composition is well rammed around and above the shell, and the sack is closed at the top. Finishing. The bottom of the sack is protected from the force of the charge by an iron cup (a), called a cwfo^, and the whole is covered and strengthened with a net- work of spun-yarn, or wire, and then overlaid with a composition of pitch, rosin, cfec. 374 PYROTECHNY. FIKEWOEKS FOE LIGHT. , A fire-ball is primed by driving into the top of the composition a greased wooden pin about three inches deep, and filling the hole thus formed with fuze com- pjositioQ, driven as in a fuze ; space is left at the top of each hole for two strands of quick-match, which are fastened by driving the composition upon them. The fuze-hole is covered with a patch saturated with kit composition, which is a mixture of rosin, beeswax, pitch, and tallow. 383. Light-ball. Light-balls are made in the same manner as fire-balls, except that, being used to light up our own Avorks, the shell is omitted. 384. Tarred links. Tarred links are used for lighting lip a rampart, defile, cfec, or for incendiary purposes. They consist of coils of soft rope, placed on top of each other, and loosely tied together ; the exterior diameter of the coil is 6 inches, and the interioi: 3 inches. They are immersed for about ten minutes in a composition of 20 parts oi pitch, and one of tallow, and then shaped under water ; when dry, they are plunged in a composition of equal parts of pitch and rosin, and rolled in tow or saw- dust. To prevent the composition from sticking to the hands, they should be previously covered with linseed oil. How used. Two links are put into a rampart grate, separated by shavings. They burn one hour in calm weather, and half an hour in a high wind, and are not extinguished by rain. To light up a defile, the links are placed about 250 feet apart ; to light up a march, the men who carry the grates should be placed to the leeward of the column, and about 300 feet apart. 385. Pitched fascines. Fagots of vine-twigg, or othei* TOKCHES. 3Y5 very combustible wood, about 20 in. long and 4 in. diam- eter, tied in three places with iron wire, may be treated in the same manner, and used for the same purposes as links. The incendiary properties of pitched fascines may be increased by dipping the ends in melted rock- iire; when used for this purpose, they are placed in piles intermingled with shavings, quick-match, bits of port-fires, &c., in order .that the whole may take fire at once. 386. Torches. A torch is a ball of rope impregnated with an inflammable composition, and is fastened to the end of a stick, which is carried in the hand. Prepa/ration. Old rope, or slow-match, well beaten and untwisted, is boiled in a solution of equal parts of water and nitre; after it is diy, tie three or four pieces (each four feet long) around the end of a pine stick, about two inches diameter, and four feet long ; cover the whole with a mixture of equal parts of sulphur and mealed powder, moistened Avith brandy, and fill the intervals between the cords with a paste of three parts of sulphur and one of quicklime. When it is dry, cover the whole with the following composition : PITCH. VBJTICE TURPENTINE. TURPENTINE. 3 3 1 2 How used. Torches are lighted at the top, which is cracked with a mallet; they burn from one and a quar- ter to two hours. In lighting the march of a column, the men who carry torches should be . about 100 feet apait. 376 PYEOTEOHNY. — OFFENSIVE. ETC., FIKEWOEKS. OFFENSIVE AND DEFENSIVE FIKEWOEKS. The principal preparations of this class, employed in modern warfare, are hags of powder and Ugkt-ha/rrels. 387. Kags of powder. Bags or cases of powder may be used to blow down gates, stockades, or form breaches in thin walls. The petard was formerly employed for these purposes, but it is now generally thrown aside. From trials made in England, it has been shown that a sand-bag (covered with tar, and sanded to prevent it fi'om sticking) containing 50 lbs. of j)Owder, has, suffi- cient force to blow down a gate formed of 4-ineh oak scantling, and supported by posts 10 inches in diameter, and 8 feet apart; and a bag containing 60 lbs. of pow- der, and weighted with two or three bags of earth, has sufficient force to make a large hole in a 14-inch brick wall. The effect of the explosion may be much in- creased by making three sides of the bag of leather, and the fourth of canvas, which, should rest against the object. A suitable means of exploding bags of powder is a time-ftize, or the ordinary safety-fuze for blasting rocks. 388. JLigrSat-barrei. A light-barrel is a common pow- der-barrel pierced with numerous holes, and filled with shavings that have been soaked in a composition of pitch and rosin; it serves to light up a breach, or the bottom of a ditch. OKNAMENTAL FIKEWOEKS. 389. Object, &c. Ornamental fireworks are employed GEKBE. 377 to celebrate great events, as victories, treaties of peace, funerals, &c. They are divided mio fixed pieces, tuov- cible pieces, decorative pieces, and preparations for com- municating fire from one part of a piece to another. The different effects are produced by modifying the pro- portions of the ingredients of the burning composition, so as to quicken or retard combustion, or by introducing substances that give color and brilliancy to the flame. The fixed pieces are lances, petards, gerhes, flames, &c. 390. lance. Lances are small paper tubes from 0.2 to 0.4 in. diameter, filled with a composition which emits a brilliant light in burning (a, fig. 131). Instead of a sin- gle composition, each lance may contain two or more I'ig- isi- compositions, which, in turn, emit different-colored flames. The case should be as thin as possible, in order that the color of the flame of the composition may not be affected by that of the paper. Lances are generally employed to form figures; this is done by dipping one end in glue, and sticking them in holes arranged after a certain design, in a piece of wood-work. 391. Petard. Petards are small paper cartridges filled with powder. One end is entirely choked, and the other is left partially open for the passage of a strand of quick-match, destined to set fire to the powder. A petard is usiially placed at the fixed end of a lance, that the flame may terminate with an explosion (h, fig. 131) ; they are also used to imitate the fire of mus- ketry, 392. Gerbe. Gerbes are strong paper tubes or cases, filled with a burning composition. The ends are tamped 378 PYKOTECHNY. MOVABLE PIECES. witli moist plaster of Paris or clay; through one, a hole is bored, extending a short distance into the composi- tion, that it may emit a long sheaf or gerhe of brilliant sparks. The diameter of the case is about one inch, and the length depends upon the required time of burning. The number of blows to each ladleful of composition is ten. Gerbes are secured to the frame of the piece with wire or strong twine, and pointed in the direction that the flame is to take. Composition. MEALED POWDEE. NITRE. STJLPHUE. 1 CAST-IRON PILINGS MIXED WITH SULPHUE. 32 16 10 26.4 393. Flame. Flames consist of lance or star compo- sition, driven into paper cases or earthen vases. The diameter of the burning surface should be large, to give intensity to the flame. Lance composition is driven dry, and with slight pressure. Star composition should be moistened, and driven with greater pressure than the preceding. MOVABLE PIECES. The movable pieces are shy-i^ockets, tourhillions^saxons, jets, RoTMm candles, paper shells, Vm When V is known for a given charge of powder p' afiid projectile m', the value of V can be obtained for any other charge of powder, p, and projectile, m,', of the same calibre. This law however only holds true within cer- tain limits, or when the powder is completely consumed before the projectile leaves the piece.* 408. 'Wltat aflTects initial velocity. The principal * Tabic of Initial Velocities with service charges. Y^ P^.^. KIND OP CANNON. 6-pdr. field, 12-pdr. " 12-pdr. " howitzer, . . 24-pdr. siege-gun, .... 8-inoh siege howitzer, . 32-pdr. sea-coast gun,. . ]5-iuch columbiad CHABGB KIND OP PROJECTILE. OF POWDER. SHOT. SHELLS. sph'l case. Lbs. Feet. Feet. Feet. ■ 1.25 1439 1367 2.50 1486 1486 1.00 1054 953 COO 1680 16f0 8.00 1870 4.00 907 8.00 1640 1450 40.00 1000 Note. — When tlie initial velocities of shot, shells, and spherical-case shot are given, the weight of the charge refers to the solid shot. 388 SCIENCE OF GUNNERY. ^INITIAL VELOCITY. causes wliich influence initial velocity, are tlie character of the piece, powder, and projectile. Most of these have been considered under their appropriate heads, in treat- ing of the construction of cannon ; it will only be neces- sary, therefore, to recapitulate them here. They are the size and position of the vent, the windage, the length of the bore, the form of the chamber, the diam- eter and density of the projectile, the windage of the cartridge, and the form, size, density, and dryness of the grains of powder, and the barometric, thermometric, and hygrometric states of the atmosphere. It has been found by late experiments that the initial velocity is unaffected by the angle of fire. Theoreti- cally, varying the weight of the piece should exert an influence on the initial velocity ; but, in consequence of the great disparity of the weight of the piece and pro- jectile, this influence is inappreciable in practice. 409. l>eteriiiiiiiatiou of initial velocity by experiment. A great variety of instruments have been invented to determine directly the initial velocity of a projectile, the most reliable of which are the gun-pendulMm, the halr listic pendulMm, and the electro-hallistiG onachines. In the first, the velocity of the projectile is determined by suspending the piece as a pendulum, and measuring the recoil impressed on it by the discharge ; the expres- sion for the velocity is deduced from the fact, that the quantity of motion communicated to the pendulum is equal to that communicated to the projectile, charge of powder, and the air. The second apparatus is a pendu- lum, the bob of which is made strong and heavy, to receive the impact of the projectile; and the expression for the velocity of the projectile is deduced from the THE WEST POINT BALLISTIC MACHINE. 389 fact, that the quantity of motion of the projectile before impact is equal to that of the pendulum and projectile after impact. These machines have been carried to great perfection, both in this country and France, and very accurate and important results have been obtained by them; but they are very expensive, and cannot be easily adapted to the various wants of the service. The employment of electricity to determine the veloc- ity of projectiles, was first suggested by Wheatstone, in 1840. The application depends on the very great veloc- ity of electricity, which, for short distances, may be considered instantaneous. The general method of apply- ing this agent is by means of galvanic currents, or wires, supported on target frames, placed in the path of the projectile, and communicating with a delicate time- keeper. The successive ruptures of the wires mark on the time-keeper the instant that the projectile passes each wire, and knowing the distances of the wires apart, the mean velocities, or velocities at the middle points, can be obtained by the relation, velocitY= -£ •^ ' •' time The various plans in use differ only in the manner of recording and keeping the time of flight ; one of the simplest and most common instruments employed is the pendulum. The ballistic machine of Captain Navez;, of the Belgian service, has been tried in this country, but has been found too delicate and complicated for general purposes. * In consequence of the variable nature of the resistance of the air, this mean velocity does not strictly correspond to the middle point between the targets. The difference, however, is very slight, as is shown by Captain Navez in the case of.a 6-pdr. ball moving with an initial velocity of 600 meters, over a space of 50 meters; the difference between the mean velocity and the velocity which it should have at the middle point, is only 0.05 meter. 390 SCIENCE OF GUNNEET. INITIAL VELOCITY. 410. Ttae We§t Point ballistic machine. Fig. 132 represents the front and end views of an electro-ballistie machine originally devised by the author for the nse of the Military Academy, and since adopted by the ord- nance department, for proving powder, &c. Fig. 132. a is a bed-plate of metal, which supports a graduated arc (b). This arc is placed in a vertical position by means of thumbscrews and spirit-levels attached to it ; and it is graduated into degrees and fifths, commenc- ing at the lowest point of the arc, and ending at 90°. pp' are two pendulums having a common axis of motion, passing through the centre, and perpendicular to the plane of the arc. The bob of the pendulum p' is fixed, but that of p can be moved up and down with a thumb-screw, so as to make the times of vibra- tion equal. m and m' are two electro-magnets attached to the horizontal limb of the arc, to hold up the pendulums when they are deflected through angles of 90°. s and s' are pieces of soft iron attached to the pro- longations of the suspension-rods, in such way as to be THE WEST POINT BALLISTIC MACHINE. 391 in contact with the lower poles of the magnets, when the pendulums are deflected. d is an apparatus to record the point at which the pendulums pass each other, when they fall by the breaking of the currents which excite the magnets. It is attached to the prolongation of the suspension-rod j?', and consists essentially of a small pin enclosed in a brass tube; the end of the pin near the arc has a sharp point, and the other is terminated with a head, the sur- face of which is oblique to the plane of the arc. As the pendulums pass each other, a blunt steel point at- tached to the lower extremity of the suspension-rod ^, strikes against the oblique surface of the head of the pin, which presses the point into a piece of paper clamped to the arc, leaving a small puncture to mark the point of passage. An improvement to the foregoing consists in attaching to the pendulum^' a delicate bent lever, which carries on its point a small quantity of printer's ink ; the pendulum p presses upon this lever, causing the point to touch the arc and leave a small dot opposite to the point where the pendulums pass each other. The magnets are also so arranged that they can be transposed from one pendulum to the other, thereby affording the means of correcting errors arising from in- equalities of magnetic power, by taking a mean of two observations, c c and c' c' represent the wires which con- duct the two electric currents to the magnets m and m'. Ta/rgets. The targets are two frames of wood placed so as to support the wires in a position to be cut by the j)rojectile. For the purpose of obtaining the initial ve- locity, the first should be placed about 20 feet from the muzzle of the piece, that the flame may not break the 392 SCIENCE OF GUNNERY. INITIAL VELOCITY. current before tlie projectile readies it; the position of the second depends on the velocity of the projectile. For cannon, it should be placed about 100 feet from the first target; and for small-arm and mortar projectiles, about 50 feet. The number of times that the wire should cross the targets depends on the size of the pro- jectile and the accuracy of its flight. Currents and hatteries. The magnets should be made of the purest attainable wrought iron, in order that they shall retain no magnetic force after the exciting currents are broken ; and for this purpose they are best made of bundles of wire. The batteries should be of nearly equal power and constancy, in order that, in case the magnets do retain a portion of their magnetism, the remaining portion may be as uniform as possible. Grove's or Bunsen's batteries are the best that can be used for this purpose. The power of the battery is regulated by the distance of the targets and the size of the conducting wires. If a weak battery be used, the magnetic power may be increased by increasing the diameter of the wire, or by resting pieces of soft iron' on the upper poles of the magnet. In experimenting with cannon, the machine should be placed about 120 yards from the piece, to prevent any disturbance from the discharge; at this distance the record will have been made before the sound reaches the machine. For this distance, three cups, in which the zinc cylinders are 8 inches long and 3 inches diameter, and an insulated copper wire .06" diameter, have been found to answer a good purpose. The disjunctor. The disjunctor is a small auxiliary instrument for closing and breaking the currents at will. THE WEST POINT BALLISTIC MACHINE. 393 It affords tlie means of verifying tlie accuracy of tlie pendulnm macliine by a succession of simultaneous rup- tures of the wires; when the machine is in good condi- tion, the position of the point of meeting seldom varies a tenth of a degree, an error which corresponds to only .000154 of a second of time. When the currents are of equal strength, and the starting points are properly adjusted, the point of meet- ing will be found opposite to the zero of the grad- uated arc; if of unequal intensity, the point will he found near the zero point and on the side of the stronger magnet. As this position is nearly constant for the same currents, the error of the reading can be easily corrected. If the error be positive, subtract it ; if nega- tive, add it. I Arrangement, c&c. Figure 133 shows the working arrangement of the several pieces : a represents the pen- dulum; i the disjunctor; c c and c' c' the currents ; e e' the batteries ; and d the position of the gun. To operate them, the disjunctor is closed, the pendulums are deflected, the marking- pin revolved perpendicular to the arc, the piece is fired, and the position of ^'s- 1^^- the puncture in the paper, with reference to the grad- uated arc, noted. To determine the time. The velocity of the electric currents being considered instantaneous, and the loss of power of the magnets simultaneous with the rupture of the currents, it follows that each pendulum begins to move at the instant that the projectile cuts the wire, and that the interval of time corresponds to the differ- 394 SCIENCE QE GUNNERY. INITIAL VELOCITY. ence of the arcs described by tlie pendulums up to tlie time of meeting. Let in andm^, fig. 134, represent the positions of the two magnets, and let the interval between the rupture be such that the centres of oscilla- tion will pass each other at i. As the times of vibration are equal, the interval of time will correspond to the arc i i', the arc m' i being equal ^Jg- 134. to m i'. A vertical line through the centre of motion bisects the arc i i'. The reading therefore corresponds to one-half of the required time, or time of passage of the projectile between the wires. To determine a formula for the time that it takes for one of the pendulums to pass over a given arc, let I be the length of the equivalent simple pendulum, v the velocity of the centre of oscillation or point m\ y the vertical distance passed over by this point, x the vari- able angle which the line of suspension makes with the horizontal, and t' the time necessary for the point m' to pass over an entire circumference, the radius of which is I, with a uniform velocity v, we have, v—V'igy. Substituting for y its value in terms of the constant angle of half oscillation and the variable angle cc, the above expression becomes, v=V2glcos.{%(r—x) ; from which we see that the velocity of the pendulum increases from its highest to its lowest point, and vice versa. The time t' is equal to the circumference of the circle, the radius of which is I, divided by the velocity, v; THE WEST POINT BALLISTIC MACHINE. 395 again divide this by 360, we have tlie time of passing over eacli degree, or, ^ , ^^ %j^ 360|/2^^cos.(90"-») ■ To determine ^, it is necessary to change the cylin- drical arms of suspension to knife-edges, in order to de- termine the time of vibration through a veiy small arc. The mean of 500 vibrations will be very near the exact time of a single vibration. Knowing the time of a single vibration, the length of the equivalent simple pendulum can be obtained by the relation 1=^1' t'"^, in which f is this time, and I' is the length of fhe simple second's pendulum at the place of observation. At West Point ?'= 39.11448 inches. " " g?= 32.17050 feet. In this way all the constants of the expression for t are known, and by assigning difi'erent values to x, a table can be formed, from which the times corresponding to different arcs can be obtained by simple inspection. The table in chapter XIII. is calculated for the West Point machine. MOTION OF A PKOJECTILE IN VACUO. 411. UeterMaimation of equations of snotiona. A. pro- jectile is a body thrown or impelled forward, generally in the air ; and the trajectory is the line described by its centre of inertia. The movement of a projectile will 1 )e considered firstly in vacuo, and secondly in the air. Let A (fig. 135) be the position of the muzzle of a fire-arm, and the line A B its axis prolonged. 396 SCpiBTCE OF GTJIfNEEY. — ^MOTIOH IN VACUO. Kg. 135. Let ^ represent the angle which, this line makes with the horizontal plane, or the aihgle of projection. V the initial velocity. V the velocity at the point m. t the time of flight to the same point. Q the inclination of the tangent at this point. «, y^ thg co-ordinates of this point. JTthe horizontal range, ]Fthe greatest height of ascent. Tthe whole time of flight, or for the range X. If the projectile were only acted upon iDy the force of the discharge, it would move in the straight line A B^ and after a time, t^ would reach the point _P; but it is constantly drawn to the earth by the force of gravity, and instead of being found at the point 7^, it is found at the point ot, situated at a distance below P equal to the distance which it would fall in the same time under the influence of gravity, or ^gf'^ g being the velocity generated by gi'avity in a second of time. The distance -P6' is equal to x tan. ; the distance m(7, ory, is equal to this distance diminished to ^gf, oi', y=xian. -\gf; cc=# T^cos. -igf. (2) x= Vt cos. (^. (3) *=V^^- (4) K cos. 9 ^ ^ 2d. To determine the vertical ascent and horizontal range of the projectile, differentiate equation (1), and i)lace the value of ^=0; whence we obtain, ax X=4.IIsin.cl>cos.. (5) ^ JT being the abscissa of the highest point, Y=^sin.V. (6) The first value of JT shows, tJiai the o'ange can he ob- tained tvitJi two angles of projection^ provided they he complements of each other • the second value shows, that tlie greatest range corresponds to an angle -of 45°, and that this range is equal to twice the height due to the ve- locity ; and, also, that variations in the angle of fire produ; 9 9 398 SCIENCE OF GXTNirEET. 3I0TI0N IN VACUO, and from these we have, V _V^ (7) Therefore, under the same angle of fire, the ra/nges ari^ proportional to the squares of the velocities / and recip- rocally, the velocities are propoi^tional to the square roots of the ranges. ds 4tli. The velocity at any point is equal to -j, or 1)*=-—^ — . Substituting the values of dy and dx, obtained by differentiating equations (2) and (3), we have v^= V^-2 Vgtsm.i>-\-gH\ Substitute for-2 F^^sin.0+/i!^ its Yalue-2gy, de- rived from equation (2), we have, v'^ V'-2gy. Eeplace V^ by 2gII, and reducing, the expression be- comes, v^\/2g{JI-y). (8) This shows iJiat the velocity of a projectile, at any point, depends on its height above the inuzzle of the piece ; and that it is equal to that which is attained in falling through the height (^H—y). It also shows tJiat the ve- locity is least when y is greatest, or at the summit of tAe trajectory^' and that the velocities at the two points in which the trajectory cuts the horizontal plane are equal. 5th. The total time of flight may be determined by substituting the value of X^'^IImi.^cos.t^, equation (5), in equation (4), which becomes AlHwx.^ "Fsin.(^ (9) MOTION IN VACUO. 399 If =Vi, and F=/^ Calling T, tlie time of fliglit, we have, ' V \g V 16.07 ^ Hence the time of fiiglit for an angle of 45° is equal to the square root of the quotient cf the range divided by ofie-half of the force of gravity / or, it is approximately equal to onefourth of the square root of the range ex- pressed in feet. 6tli. The tangent of the angle made by a tangent line at any point of the trajectory is equal to -^, which is obtained by differentiating equation (1) ; calling this angle 0, avc have, tan.o=tan.r6 == . (10) ' 2// COS. 2 <^ ^ Substitute the value of jr= 4 II sin.^ cos.<;6, the angle of fall on horizontal ground is tan.9=— tan.0; that is to say, the angle of fall is equal to the angle of projection, measured in an opposite di/rection. 7th. The position of a point being given, to find the initial velocity necessary to attain it, let a and i be the horizontal and vertical co-ordinates of this point of the curve, and e its a/ngle of elevation. Substituting these quantities in equation (1), and recollecting that tan. er= -, we have, a a cos.e ~~4 sin. (. Makine; tan.(i>=o, we have, cos.2^Hl^a'- 412. Practical application of formula. The preced- ing formula will only be found to answer in practice for projectiles Avhich experience slight resistance from the air, or for heavy projectiles moving with low velocities, as is commonly the case with those of mortars and howitzers. The following table gives the difference between the observed and calculated times of flight of the French 8 and 10-inch mortar shells, weighing 64 and 119 lbs. respectively. The initial velocities being unknown, the times are calculated from the observed ranges. The observed times are invariably greater than the calculated times, as might be expected from the resist- ance of the air, which retards the motion of projectiles. PEAOTICAL APPLICATION OY FORMULA. - 401 n p. Eftnges fl irngles of Times of flight. 45° 30° 45° 30° Observed. Calcu- lated. Observed. Calcu- lated. Kilog. 0.234 Meters. 343 Meters. 290 Seconds. 9.8 Seconds. 8.4 Seconds. 6.8 Seconds, 5.8 8-incli. 0.351 0.585 629 1146 661 1011 12.9 16.0 11.3 15.3 10.0 12.3 8.1 10.9 0.994 1792 1690 20.8 19.2 16.9 14.1 0.468 457 383 11.0 9.7 7.5 6.8 0.693 734 637 14.0 12.2 10.0 8.7 10-incli. 1.054 1132 980 17.0 16.2 12.0 10.2 1.405 1655 1355 20.0 17.8 14.0 12.6 1.639 1757 1516 23.0 18.9 15.0 13.4 Tte next table sliows the observed and calculated ranges, for 30° elevation, and the observed ranges for 46" elevation, for the above projectiles, the initial veloc- ities being the same for each projectile. 1 Ranges of 10-inch Mortar Shells. Eanges of 8-ineli Mortar Shells. 45° 1 elevation. 30° elevation. 45° elevation. 30° elevation. [ Obsei*ved., Observed. Calcu- lated. Difference Observed. Observed. Calcu- lated. Difference I Meters. 457 734 1 1132 1555 1757 Meters. 383 637 980 1355 1516 Meters. 396 637 982 1350 1522 Meters. + 13 + 2 — 5 + 6 Meters. 343 629 1146 1792 Meters. 290 661 1011 1690 Meters. 298 545 993 1652 Meters. + 8 —16 — 13 —138 It appears from the foregoing tables, that the ranges of mortars with different degrees of elevation, can be calculated up to about 1,400 yards from equation (5), or, X=2.fl'sin. 2' ) ^ 1427 ft.' ^ -would nearly satisfy the results of experiments. Callina' ^=:— , and nR^ the area of the cross section of a projectile, the general expression for the resistance in air becomes, ,=A.eU + '\v\ (14) 404 SCIENCE OF GtfNNEKY. EESISTANCE OF THE AIE. In this expression^ A is the resistcmce, in pounds, on a square foot of the cross-section of a projectile moving with a velocity of one foot; r is a linea/r qucmtity de- pending on the velocity of the projectile. For all service spterical projectiles, ^=.000514; and for all service velocities ?*=!, 42 7 feet. The value of J. for the rifle- musket bullet (page 312) has beeu determined at the Washington Arsenal, by the method laid down in the note on page 411, and found equal to 0.000358. This shows that the resistance of the air is about one-third less on the ogeeval than on the spherical form of projectile. This value has been found to answer well for calculating the ranges of rifle-cannon projectiles. The coefficient A, being a function of the density of the air, its value depends on the temperature, pressure, and hygrometric condition ; in the above value the weight of a cubic foot of air = . 075 lb., at a temperature of 60° Fahr., and for a barometrical pressure of 29.5 inches. If tbe surface of th.e projectile be rongli or irregular, the value of this coefficient v^^ill be sligbtly too small. Example. — What is the pressure of the air on a 42-pdi-. shot moving ^yith a velocity of 1,500 feet? p=.000514 X 3.1415 X ^° X 1500'/ 1 + ^^ 1=629.3 lbs, / 1500\ (^^imj^ 415. Fall o£ a projectile in ttac air. Tlie motion of a body falling through the air, will be accelerated by its weight, and retarded by the buoyant effort of the air, and the resistance wliicli the air offers to motion. As the resistance of tbe air increases more rapidly than the velocity, it foUows that there is a point where the retarding and accelerating forces will be equal, and that beyond this, the body will move with a uniform veloc- FALL OP A PROJECTILE IX THE AIE. 405 ity, equal to that wMdi it had acquired down to this point. The buoyant effort of the air is equal to the -w^eight of the volume displaced, or Py- ; in which P is the weight and D the density of the projectile, and d the density of the air. When the projectile meets with a resistance equal to- its weight, we shall have, P(l--^)=^.i2v(l+^); (15) in which the weight of the displaced air is transferred to the first member of the equation. As the density of the air is very slight compared to that of lead or iron, the materials of which projectiles are made, -^ may be neglected. Making this change, and substitu- ± ting for P, -—-nli^P (g having been divided out of the o second member, should be omitted in the first), the ex- pression for the final velocity reduces to '0+^lf • (-) The resistance on the entire projectile for a velocity of 1 foot, is At:B^ ; dividing this by ■ — , or the mass, we get the resistance on a unit of mass. Calling this — , we have, 1 AnP!" „ P 9 v" 406 SCIENCE OF GUNNERY. LOSS OP VELOCITY. Substitiiting for P its value in tte equation of verti- cal descent, we have, 2^.=^^(l+^); from wliicli we see that v depends only on g / but ^=3 -gA ^1^> hence, the final velocity of a projectile falling in the air is directly proportioned to the product of its diameter and density^ and inversely piroportional to tlie density of the air, luliich is a factor of A. The expi'ession for the value of (c) shows, that the re- tarding effect of the air is less on the larger and denser projectiles. To adapt it to an oblong projectile of the pointed form, the value of i? should be increased, (inas- much as its weight is increased in proportion to its cross section,) while that of A. should be diminished. Ifc fol- lows, therefore, that for the same calihre, an ohlong pro- jectile luill he less retarded hy the air than one of spheri- cal form, and consequently with an equal and perhaps less initial velocity its range loill he greater. The value of (c) for service pi'ojectiles will be found ready calculated in the tables of fire, in Chap. XIII. LOSS OF VELOCITY BY RESISTANCE OF THE AIR. 416. Equations of motion. For the purpose of de- termining the velocity which a projectile loses by the resistance of the air, in moving through a certain dis- tance, », the force of gravity may be disregarded ; in which case the trajectory described will be a right line. LOSS OF VELOCITY BY THE AIE. 407 Let V be the initial velocity, and v the remaining ve- locity at the end of the distance on. The expression for the resistance of the air is, as we have seen, But we know that the retarding force of the air is equal to the mass of the projectile against which it acts, multi- plied by the first differential coefficient of the velocity, regarded as a function of the time, with its sign changed, and that — is the mass of the projectile. We have, therefore, KecoUecting that P^-^R^ D, and that 2c=-.^, the equation reduces to, ^_ i» - / "^X Integrating this equation between the limits and cc, which correspond to V and -y, we have, T F To obtain a relation between the space and velocity. we have ■?;=: — ^ oxdt=. — ; substitutinsc this in the equa- dt V ' ^ tion for the intensity of the retarding force, and reduc- ing, we have, dv dx=z — 2c V ■C-^), 408 SCIENCE OF GUNNERY. LOSS OF VELOCITY. Integrating between the same limits as in tlie preced- ing case, we have, r X ^=2olog.l^or l+r=/i + ^>2^" (19) Solving this equation with reference to v, we have, r v= . (20) (l+f> -1 Substituting, in equation (18), x for its value given in equation (19), we have, t=2G (^-1-)-^. (21) \v v/ r The logarithms in the above equations belong to the Napierian system, and are obtained by multiplying the corresponding common logarithm by 2.3026:6=2.*?13. Practical remarTcs. Equation (19) gives the space passed over by a certain projectile when the velocities at the commencement and end of the flight, are known. Equation (20) gives the remaining velocity when the initial velocity and the space passed over are known. Equation (21) gives the time of flight when the idion'§ method. Captain Didion, professor of gunnery in the artillery school at Metz, howevei-, furnishes an approximate solution to this difficult ques- tion, which may be used in practice. To do this, he considers the resistance of the air equal to Anli'{l+-\v'; and by assuming a mean value for the different inclina- tions of the elements of the trajectory to their horizon- . . . ds tal projections, which makes -^ constant, he is able to 2c Since y is the same for all the distances, wo have 2c X 2,c 1x , r V r v' r ' ~7/l 1 \y v' From the note on page 389, we are at liberty to place f^— and v'= — - substitut- t t ing these values in the preceding equation, reducing and changing the signs of both numerator and denominator of the second member, we have 2x(f—i+^ t"—'l( "Which equation gives the value of c in terms of t, t', i'\ and which can bo deter- mined by taking the mean of several shots, with the eleotro-ballistio machine, at the different distances, x, 2x, and ix. didion's method. 413 integrate tlie differential equations, and place them un- der the following forms : (I ^ T, ^ 2 F'' COS. ' CO Tan. e— t&a. = 10 , differs only about 0.01 from unity ; and this expression V may be reduced to — . When the angle of projection does not exceed 3", cos. ^ differs only .001 from unity, and we can everywhere replace V^ cos. ^ by F". Under COS. ^ this angle, — '— differs but slightly from unity, and we V . . ■ . have v=^ —=, which is the same as if motion took place in a horizontal plane. All cases of the movement of projectiles which occur in practice, may be divided into three distinct classes : 1st, When the angle of projection is slight, or does not exceed 3°, as in the ordinary fire of guns, howitzers, and small-arms ; 2d, When the angle of projection is greater than this, but does not exceed 10° or 15°, as in ricochet fire, &G. ; 3d, When the angle of projection exceeds 15", as in the fire of mortars. 422. i§t Class. M)?^ small angles of projection, as in guns, liowitzers, and small-arms. For slight variations of the angle of projection above or below the horizon, the form of the trajectory may be considered constant ; and when the object is but slightly raised above, or depressed below the horizontal plane, it may be considered as in this plane. In consequence of the windage, and the balloting of FIKST CLASS. 415 the projectile wMcli results from it, the projectile does not always leave the bore in the direction of the axis. The angle formed hy the line of departure and the axis of the piece, is called the angle of departure. For guns in good condition, the vertical deviations do not exceed 5', and for howitzers 10'; the side deviations never ex- ceed 4' 30". To obtain exact results, therefore, it is necessary to correct the angle of projection for the angle of departure, when the latter is known. T- 1 1 • • 1 1 COS. (/) under the supposition that o, cos. , and are each equal to unity, the equations of the trajectory in air may be reduced to — y^xi'^^.4>-l^.B; (22) Tan.0=:tan.0-j7-|./; (23) t=-yJ); (24) v=^. (25) Knowing the weight and diameter of the projectile, v can be calculated by the formula c=^- ■- if it be ?,gA not found in the table which accompanies it. We X V know - and — , and by means of the tables can deter- mine the desired values of JS^ I, D, and IT. Of the three things, the initial velocity, V, the dis- tance of the object, JC, and the angle of projection, ^, two being known, to determine the third. 1st. To determine the angle of projection, (p. — Make ^=0 in equation (22), and solt'e it with reference to 416 SCIENCE OF .GUNNERY. TEAJECTOKY IN AIE. tan. 0, we have, Example. — Find the angle of projection necessary to throw a 12-pdr. shot 1800 feet, with an initial velocity of 1500 feet. "We have F=1500 feet; - = ^=0.5336 ;—= ^=1.054. From ' c 3370 ' r 1427 32 17 1800 Table (1), ^=1.449; tan. 0=—-—. ==^1.449. =0.01864. ^ = roo'. 2d. To determine tlie initial velocity, V, make y=0, in equation (22), solve it with reference to Y, and mul- tiply both members by -, we have. V V^ r V 2tan.^~2'- Having the values of — and q, seek in table (5) for G X V the -^^alue of — , the value of — , which gives that of o',- c r ' multiply — by 1427 and we shall have V. r Example.— ¥'mdi the initial velocity of a 12-pounder shot which, fired under an angle of 1° 05', has a range of 1800 feet. 1 / 16.08x1800 ^-U27V 0.01864 ='■''''■ V — = 1.05. F=1.05 X 1427 = 1498.35 feet. r 3d. To determine the range, X. — Make y=0 in equa- tion (22), obtain the value of X, and divide both mem- bers of the equation by c, we have, X J. tan.0 V^ « 0^9 FIRST CLASS. 417 Having the initial velocity, V, and angle of projec- tion, ,p, we can determine, — andp; seek in table (4), for the value of—-, that of—, vs^hich gives p; having ' G --, multiply it by o, and we have X. Example. — Find the range of a 12-pdr. ball, fired under an angle of 1° 05', with an initial velocity of 1500 feet. Y c=3370;— -=1.0611; tan. ^=0.01864. r 001864 1500^_o„4 (f^.^^ t^^lg 4),^ = .5340;X=.5340 3370 16.08 ' ^ ' c X 3370=1800 feet. The slight discrepancies in the three preceding results, arise from the neglected decimals. In firing spherical case-shot, it is important not only to know the time of flight, in order to regulate the faze, but it is important to know that the projectile will have sufficient remaining velocity to render the impact of the contained projectiles effective. 4th. The time of flight can be obtained from equa- tion (24), or, t=z -=^D. Knowing — and — , we can ob- V or tain the corresponding value of D from table (3). Example. — Find the time of flight of a 12-pdr. spherical case-shot for a distance of 1500 yards, the initial velocity being 1500 feet. X 4500 , „„. V 1500 T _., n ^ „,. — ;= =1.33o: — = = 1.051 : x' = 1.859. c 3370 r 1427 i=1^1.859=5.58 seconds. 1500 5th. The remaining velocity can be obtained from 27 418 SCIENCE OF GUKNEKT, TEAJEOTOBT IN AIR. equation (25), or, v=-==. Knowing — and — , ol)tain U or from table (3) the corresponding value of U. Example — Find the remaining velocity of a 12-pdr. spherical case- sliot at the distance of 1500 yards, the initial velocity being 1500 feet. ^=1^0=1.327; -1=1.051; ^=2.882; . ^^^^ =520 feet, c 3370 r ' 2.882 This velocity is more than sufficient for a musket-bullet to disable an animate object at the distance of 1500 yds. 423. 2d class. _Z^r angles of projection Tiot exceed- ing 10° or 15", as in the ricochet fire of guns^ howitzers, and morta/rs. The formulas are : y=a? tan.0— ^ -^^=5 ^B (26) tan..=.tan.0-<7-p.-,— ^Z (27) *=v-^^- (28) v=-jf 1- (29) Ucos.d ■ If the object be on a level with the piece, the solu- tion of this class of jaroblems is the same as those of class 1st, when the angle is very small ; if not, it Avill be necessary to substitute for V, V^ — T^cos. , which gives V. The object being situated at the distance a from the piece, and at the distance b above the horizontal plane passing through the centre of the muzzle, is seen undei' an angle of elevation e, for Avhich tan.e=:-. One of the SECOND CLASS. 419 two things, tlie initial A^elocity or angle of projection 1 leing known, to determine the other. 1st. To determine the initial velocity^ V. Substitute in equation (26) the co-ordinates a and 5, and V^; solve it with reference to V-^ ; substitute tan, e for -, and di- vide both members by r, we have, F .1 / f^ V£ ry tan.^— tan.e ^' Having the value of q, seek in table (5) for the known value of -, the value of —i- corresponding to it, and mul- c f. ^ ° ' tiplying by we shall have V. COS-ii^ Example. — Find the initial velocity of an 8-incli siege-howitzer shell, which, being fired under an angle of 12°, will strike an ohject situated 1,000 feet from, and 20 feet above, the muzzle of the piece. 20 Tan.0=O.2125; tan.e=—— -=0.0200; tan.^i — tan.£=0.1925 ; cos.0=O.9781; ^=3^°=0.2801; g^^^ I 16.08 .JIOOO \j 0.1925 ~° V ,, 0.2150. 1427 „,„ - ^ 0.2023; -^=0.2150; ^= — ^^^gl - = 3^3 feet. 2d. To determine the angle of projection. The result will be sufficiently near the truth, if we substitute, in equation (26), Ffor F^ , or Y cos. ^ ; and solving it with reference to tan. (/>, we have, tan.0=tan. e+^^B, in which we substitute for JS its value, coiTesponding to _ and — obtained from table (1), c r 420 SCIENCE OF GUNNERY. TKAJECTORY IN AIE. -Ebamp/e.*— What angle of projection is necessary for an 8-inch siege-howitzer shell to strike an object situated 1000 feet from, and 20 feet above, the muzzle? The initial velocity being 313 feet, ^ „ a 1000 V 313 20 F=313 feet; -= ---= 0.2801 ; - z=_-=0.2193 ; tan.e= c 3S70 ■ ' r 1427 ' ' 1000 16.08.1000 , , , =0.0200 ; tan. (4=:0.0200-l- 1,142=0.2084 ; =llo 28 . SIS'* 424. 3d class. Properties of trajectories under high angles of projection. As a projectile rises in the ascending brancli of its trajectory, its velocity is diminislied by tlie retarding effect of the air and tlie force of gravity : in consequence of the resistance of the air alone, the velocity continues to diminish to a point a little beyond the summit of the trajectory, where it is a minimum ; and from this point it increases, as it descends, under the influence of the force of gravity, until it becomes uniform, which event depends on the diameter and weight of the pro- jectile and the density of the air, or, in other words, upon the value of c. The inclination of the trajectory decreases from the origin to the summit, where it is nothing ; it increases in the descending branch from the summit to its ter- mination, and if the ground did not interpose an ob- stacle, it would become vertical at an infinite distance. An element of the trajectory in the descending branch has a greater inclination than the corresponding element of the ascending branch. Strictly speaking, the trajectory in air is an expoten- tial curve with two asymptotes; iih.Q first is the axis of the piece, which is tangent to the trajectory when the initial velocity is infinite ; the second is the vertical line toward which the trajectory approaches as the horizon- THIRD CLASS. 421 tal component of the velocity diminislies, and the effect of ithe force of gravity increases. The curvature of the trajectory increases in the as- cending branch, to a point a little beyond the summit. The point of greatest curvature is situated nearer the summit than the point of minimum velocity. In the fire of mortar shells under great angles of pro- jection, and at customary distances, the trajectory may be considered as an arc, in which the angle of fall is slightly greater than the angle of projection. In the ascending branch, the arc commences under an angle of ^, and terminates under an angle of ; the ratio of the length of this arc to its projection, or a, is calculated for all arcs from 5° to 75", and arranged, in groups of fives in the accompanying table. The value of a is considered the same in the descend- ing as in the ascending branch. ARCS. a ARCS. a ARCS. a 6° 1.00127 .30° 1.05306 55° 1.27583 10 1.00516 35 1.07596 60 1.38017 15 1.01184 40. 1.10730 65 1.53433 20 1.02165 45 1.14777 70 1.77772 25 1.03514 50 1.20189 75 2.20349 The multipliers, B, I, D, and the divisor, £/", are cal- culated for the values -^ and -', and they are em- G r •' ployed in equations (26), (27), (28), (29), as in the preceding class of cases. 1st. Find the initial velocity of a mortar shell, hnow- ing the range and angle of projection. We knovy — , and by solving equation (26) as before, G 422 SCIENCE OF GUNNERY. TEAJECTOEY IN AIE. we have, r r \ tan.^ ^ Having determined the value of q, seek in taUe (5) the value of — 'corresponding to it for — ; then multiply it by , and we have V. ^ •' •' aCOS.(f> Example. — What initial velocity is necessary to project a 10-inch shell 1,800 feet, under an angle of 45°? For a 10-inch shell, c=z4677; for 45", a = 1.148; — = 1.148.1800 1.148 / 16.08.1800 = 04418- ff= \/ = 0.1369. By the 4677 "•'''tiB. 1— 1427 y i.ooOO ^ aV aid of table (5) we find ^=0.1490 : and from tWs we get „ 0.1490.1427 „„„. ^ V= -— - =202 feet. 1.148.0.7071 2d. To determine the angle and velocity of fall, and the time of flight, Tcnowing the initial velocity and range. Let the projectile be the same as in the preceding case. Uxamvle. — We have — =0.4418 : and ^=0.1490; from ta- c r ble(l) wo have 7=1.291; from table (2), i?=l. 127 ; and ^7=1.272. Substituting the proper values in equation (25) we have Tan.0=.l.OOOO-^^^^-^^.1.28O=-1.159;9=_49°12'. The negative sign indicates that the angle of fall is measured in an opposite direction from the angle of projection. Making the proper substitutions in equations (28) and (29), we have -" '''' -1.127 = 10.95". .=^--^^-l= 222 feet. 262.0.7071 1.272.0.6534 3d. To determine the range, hnowing the initial ve- locity and angle of projection. TRAJECTOKY OF OBLONG PKOJECTILE. 423 aV We have a, and — ;-'; make y=o in equation (26) ; solve it witli reference to JT, and multiply both mem- hers by — and we have, aJi -r, aV . — jo= sm. 2(b=p. go ^ Having found the value of — , which for — '- gives f (table 4) ; multiply it by — , and we have X. a Example. — Find the range of | a 10-incli mortar shell, the angle of projection of ■which is 45°, and the initial velocity is 262 feet. aV Cos. ^^O.VOVl ; the sin. 2(/)=1.0000; anda=1.148; — ■' = 1.148. 262. 0.V071 aV'^ . 1.148. "262 —-r = 0.1490 ; »= — sin.2 \ which the length of the fuze is regulated, is to take tha square root of the range in feet, and divide it by four ; the quotient is the approximate time in seconds. Stone-mortars are pointed in the same manner as common mortars : the angle of fire for stones is from 60° to 75", in order that they may have great force in falling; the angle for grenades is about 33°, in order that their bursting effect may not be destroyed by their penetration into the earth. 439. Wigiit-fflrimg. Cannon are pointed at night by. means of certain marks, or measurements, on the car- riage and platform, which are accurately determined during the day. In the case of guns and howitzers, the elevation may be determined by marking the elevating screw where it enters the nut, or by measuring the distance between the head of the screw and stock. In the case of mortars, the position of the quoin may be determined by marking, or by nailing a cleat on the bolster. The direction of a carriage or mortar-bed is detei-- mined by nailing strips of boards along the platform, as guides to the trail and wheels ; to prevent the strips from being injured by the recoil, they should be nailed at a certain distance from the carriage, or bed, and the space filled up with a stick of proper width, which should be removed before firing. The chassis of a sea- coast carriage can be secured in a particular direction by firmly chocking the traverse wheels. GEADITATION OF KEAE-SIGHTS. 445 440. Pointing small-armis. The rear-sights of small- arms are graduated witli elevation marks for certain distances, generally every hundred yards; in aiming with these, as with all other arms, it is first necessary to know the distance of the object. This being known, and the slider being placed -opposite the mark corre- sponding to this distance, the bottom of the rear-sight notch, and the top of the front sight, are brought into a lino joining the object and the eye of the marksman. The term coarse-sight is used when a considerable por- tion of the front-sight is seen above the bottom of the rear-sight notch; and the term fine-sigJit, when but a small portion of it is seen. The graduation marks being determined for a fine-sight, the effect of a coarse-sight is to increase the true range of the projectile. 441. Graduation of rear-sigiits. If the form of the trajectory be known, the rear-sight of a fire-arm can be graduated by calculation; the more accurate and reli- able method, however, is by trial. Suppose it be re- .. quired to mark the graduation for 100 yards; the slider is placed as near the position of the required mark as the judgment of the experimenter may indicate; and, ^^'itK this elevation, the piece is carefully aimed, and ilrod, say ten times, at a target placed on level ground, ;it a distance of 100 yards. If the assumed position of tlie slider be correct, the centre of impact of the ten shot-holes will coincide with the point aimed at ; if it be incorrect, or the centre of impact be " found below the point aimed at, then the position of the slider is too low on the scale. Let P be the point aimed at, and P' the centre of impact of the cluster of shot-holes; we have, from close similarity of the triangles, A'F: FP:: 446 LOADma akd PorNTDsra fiee-aems. Kg. 144. A' A" : PP', from which we can determine A' A", the quantity that must he added to AA', to give the cor- rect position of the graduation mark for 100 yards. If the centre of impact had been above P, the trial mark ■would have been too high. Lay off the distance A A" above A", on the scale, and we obtain an approximate graduation for 200 yards, which should be coiTected in the same Avay as the preceding, and so on. The dis- tance J^JP' is found by taking the algebraic sum of the distances of all the shots from the point P, and dividing it by the number of shots. It will be readily seen that an approximate form of the trajectory may be obtained by drawing a series of lines through the different grad- uation marks of the rear-sight, and the top of the front- sight, and laying off from the front-sight, on each line, the corresponding range. The points thus determined are situated in the required trajectory. 442. Distance of object. Various instruments have been devised to determine the distances of objects, based on the measurement of the visual angles subtended by a foot or cavalry soldier, of mean height, at different distances ; but these instruments are considered of little practical value, especially in the excitement of action. Every officer and soldier should be taught to estimate distances by the eye, and in so doing much assistance is derived from knowing what parts of a soldier's dress, or equipments, are visible at certain distances. These data vary with the power of the eye, and each soldier should TABLES OF FIRE. 447 be required, by comparison and reflection, to create a standard for bis own. In firing cannon, tbe point at which the projectile strikes the ground or bursts, can generally be observed, and from it, the eiTor of aim can be corrected in a few fires ; this, howevei-, does not hold true for small-arm projectiles, which are seldom seen to strike the ground, unless the soil be dusty. In the defence of sea-coast batteries, the distances of objects may be determined by their proximity to known objects, as fixed buoys, or by their bearing with refer- ence to prominent landmarks. Plane-taljles may be also used to determine the distances of objects. The degree of accuracy with which the distance of an object should be known, depends somewhat on the size of the object and the inclination of the trajectory to the line of sight ; if the object be large and the trajec- tory vary but slightly from the line of sight, it is not necessary to know the exact distance, provided the aim be accurately taken. TABLES OF FIRE. 443. Purpose. The nature and purpose of a table of fire should be explained in connection with the sub- ject of pointing cannon. A properly constructed table of fire, for a particular piece, contains the range and time of flight for each elevation, charge of powder, and kind of projectile. Its purpose is to assist the artillerist in attaining his object without waste of time and am- munition, and also when the effect of shot cannot be seen on account of the dust and smoke of the battle- 448 LOADING AND POINTING FIEE-AEMS. field. The first few shots generally produce a great cfi'ect on the enemy, and it is very important that they yhould he directed with some knowledge of their results, which, in the field, can only be attained by experience, or from the data afiforded by a table of fire. The following is the form of a table of fire for guns and howtzers : j KIND OF POWDER. PROJECTILE. ELEVATION. RANGE. TIME. 1 ORDNANCE. Lbs. Lbs. ' Yards. Sec'ds. 1 1 H 29, (solid.) 5° 0' 2099 7.5 1 1' 0' 2894 9.1 10° 0' 3700 11.6 Armstrong gun, 12° 0' 4196 14.2 4-inch bore. 15° 0' 4776 17.1 20° G' 6070 21.4 25° 0' 6580 25. 30° 0' 7555 31. 1 35° 0' 9000 The ranges in the foregoing table were determined at West Point, in 1860, and are the mean of five shots for each angle of elevation. The ranges obtained with the best American muzzle-loading rifle-cannon compare favorably with these. Tables of fire, for the different service cannon, may be found in the Ordnance and Artillery Manuals, and the XIII. chapter of this work. RAPIDITY OF FIRE. 444. J>epends on size of piece, &c. The rapidity with which cannon can be loaded and discharged depends on the size of the piece, the construction of the carriage, and the care required in aiming. DEPENDS ON SIZE OF PIECE, ETC. 449 Field-cannon. Field-cannon can be discharged witli careful aim, about twice per minute ; in case of emer- gency, wben closely pressed by tlie enemy, canister-shot may be discharged four times per minute. The 12-pdr. l)oat-howitzer of the navy, with experienced gunners, can be discharged at the rate of sixteen times per minute. Siege-cannon. Siege-guns are generally discharged about twelve times per hour ; if necessary, they can be discharged as rapidly as twenty times per hour. Iron cannon can be fired more rapidly than bronze, as the latter metal is softened by the heat, and the piece is liable to bend. Siege-mortars can be conveniently fired twelve times per hour, and more rapidly than this if the object be large, as a city. Siege-howitzers can be fired about eight times in an hour. Sea-coast cannon. The fire of a sea-coast cannon de- ])ends much on the ease with which its carriage can be manoeuvred. The heaviest, or 15-in. gun, mounted on the new iron carriage, can be loaded and fired in 1' 10"; the time required in aiming depends on the angle through which the chassis is to be traversed, and piece elevated, or depressed ; it can be traversed through an angle of 90° in 2' 20". Small-arms. Muzzle-loading small-arms can be dis- charged two or three times in a minute, and breech-load- ing arms about ten times; the revolver can be dis- charged much more rapidly for six shots. This quality of a military fire-arm should be carefully guarded, as it is found that soldiers are prone to dis- charge their pieces in the excitement of battle without taking proper aim, and consequently to waste their ammunition. 29 450 DIFFERENT KINDS OF FIRES, CHAPTER X. DIFFEREliT KINDS OF FIRES. 445. Classification. Artillery fires are distiiiguisliecl by the manner in wliicli tHe projectile strikes tlie ol)- ject — as direct^ ricocliet, roll'i{ng^ and plunging fires ; by the nature of tlie projectile, as solid sliot, ahell, shrapnel, grape, and canister fires; and by the angle of ele- vation, as horizontal fire, or the fire of guns and how- itzers under low angles of elevation, and vertical fires, or the fire of mortars, under high angles of elevation. ■i46. Direct flrc. A fire is said to be direct when the projectile hits its object before striking any inter- mediate object, as the surface of the ground, or water. This species of fire is employed where great penetration is required, as the force of the projectile is not dimin- ished by previous impact ; it is necessarily employed for spherical-case shot, and for rifle-cannon projectiles, which, from their form, are liable to be deflected, by previously striking a resisting substance ; it is also used for all field-cannon projectiles, when the nature of the ground does not insure a regular rebound. To point apiece in direct fire, bring the line of sight to hear upon the object, a/nd tlien elevate tlie piece accord- iitig to the distance. 447. Ricochet fire. When a projectile strikes the ground, or water, under a small angle of fall, it pene- trates obliquely to a certain distance, and is then re- EICOCHET FIRE. 451 fleeted at an angle greater than the angle of fall ; the reason for this is, that the projectile, in forming the farrow, loses a portion of its velocity, making the distance from A (jfig. 145), the point at Fig.* 145. which it enters the ground, to O, or the vertical drawn through the deepest point, greater than the distance from O to D, the point Avhere it leaves the ground. , As this recurs every time the projectile strikes the ground, it follows that the trajectory is made up of a series of rebounds, or ricochets, each one shorter and more curved than the preceding one. The number, shape, and extent of the ricochets, de- pend on the nature of the surface struck, the initial velocity, shape, size, and density of the projectile, and on the angle of fall. A spherical projectile ricochets Avell on smooth water^ Avhen the angle of fall is less than 8°, but if the sui'face of the water be rough, very little dependence can be j)laced on the extent of the ricochet. Captain Dahlgren cites a case as coming under his obsei'vation where the distance between the first and second rebound was in- creased from 400 to 800 ya.rds by a strong wind ; at the same time, the height of the highest point of the curve was increased from a very small distance above the water, to more than 50 feet, which would have ren- dered it ineffective against the hull of a ship. From the same causes the lateral deviations in ricochet fire will be very considerable, amounting, in some cases, to between 100 and 200 yards in the entire range. In general, those projectiles which pi-esent a unifonn 452 DIFFEEEIJ^T KINDS OF FIKES. surface, and have the least penetrating power, are most suitable for ricochet firing ; hence, large shells fired with small charges are more suitable than solid shot, and round projectiles more suitable than those of an oblong form. The distance at which the larger size shells will ricochet on water is about 3,000 yards, the axis of the piece being horizontal and near the water. WTiere used, <&g. Eicochet fire is employed in siege operations to attain the face of a work in flank, or in m''^4m>,m^- Fig. 146. i-everse (see fig. 146), and on the field, or on water, when the object is large and its distance is not accu- rately known. The character of ricochet fire is determined by the angle of fall, or the angle included between the tan- gent of the trajectory and horizon at the point of fall. There are two kinds of ricochet fire — the flattened, in which the angle of fall is between 2" and 4° ; and the curvated, in which the angle of fall is between 6" and 15°. The principal pieces employed in ricochet fire in siege operations are the 8-inch howitzer, and the 8 and 10-inch common mortars; the first two may be used when the angle of fall is less than 10°, and the 10-inch mortar when the angle of fall is less than 15° — ^the proper elevation being given to the mortar by raising the rear portion of the bed. With these pieces, the PRACTICAL EULES ITOE RICOCHET FIRE. 453 limit of ricochet is about 600 yards. Solid shot should uot be used iu ricochet fire for any distance less than 200 yards, as it would then l)e necessary to diminish its velocity so much as to destroy its percussive effect. In ricochet firing against troops in the open field, the angle of fall should not exceed 3". 448. Practical rules for ricocliet Arc. In enfilading the face of a work, the form of the trajectory and point of fall should be such that the projectile will strike the surface of the terreplein the greatest number of times ; the object being to destroy the men, carriages, and traverses situated upon it. To do this, the projectile should be made to graze the crest of the adjacent parapet, and strike the terreplein as near the foot of the interior slope as possible ; the distance of the crest, and its height above the terreplein and battery, should therefore be known. The formulas in chapter VIII. furnish accurate means for calculatino- the various elements of licochet fire, but they are too complicated for use in the field ; it is there- fore proposed to deduce simple and practical rules for this purpose. 1st. To find the angle of arrival. The angle of arri- val is the angle which the tangent to the trajectory at the crest of the parapet makes with the horizon. Let A be the crest, and H the point of fall (fig. 147); the distance A JB being short, the portion of the trajectory included be- ^' ■ tween these two points may be considered a right line, and the angle of fall 454 DIFFERENT KINDS OF FIEES. and arrival will be equal. Calling a tlie angle of fall, anc\ erecting tlie perpendicular B (7, we have, . . BO or, the tangent of the angle of arrival is equal to the ver- tical distance of the point of fall helow the crest, divided l)y the horizontal distance. WitMn tlie limits of ricochet fire, the angles may be supposed proportional to their tangents; calling the tangent of 6" (which is 0.1051) 0.1, we have the follow- ing proportion : «:6..|g:0.1. or, a=60'':^, AC or, the angle of arrival is equal to 60° multiplied hy the ratio of the horizontal and vertical distances of the point of fall from the crest of the parapet. This rule gives the angle of arrival without the aid of a table of natural tangents. 2d. To find the angle of fire. The distance of the parapet is always known, and the angle of elevation of the crest can be determined by sighting along the long branch of a gunner's quadrant, and observing the posi- tion of the plummet on the arc. In consequence of the nearness of the object, and the large size and low initial velocity of the projectile, the resistance of the air in this species of ricochet fire may be neglected, which makes the trajectory a parabola. In this case the angle of fall is equal to the angle of fire, when the object is situated in the same horizontal plane PRACTICAL KULES FOll KICOOHET EIRE. 455 ^vith the piece ; if it be not in the same horizontal plane, \et £ A M (fig. 148), which is the angle of elevation Pig. 148. of the crest, be represented by e. As the angle e is very small, we are at liberty to suppose CA B—A B C. Through the point B draw the horizontal line B i>, the angle G B D is equal to the angle of arrival a; the lines^Z>and^ iltf being parallel, the angle yl B D=e; therefore C A B — OB A=a+e, but the angle CA M =:C A B-\-e^a-{-2e : or, the angle of fire is equal to the angle of arrival increased hy twice the angle of elevation of the crest of the parapet. From the erroneous suppositions made in the course of the preceding demonstrations, it will be seen that the rules deduced should give too great an angle of fire. In practice, this angle should be somewhat greater than the true angle, in consequence of the deviations, which render the projectile liable to strike against the parapet, and, of course, destroy its effect. 3d. To find the charge. When a projectile moves in vacuo, we have seen that the distance which it falls below the line of fire, .in the time t, is \ gt ^ ; and for a given distance, t is inversely proportional to the initial velocity V ; hence the distances which the same pro- jectile, fired with different velocities, would fall below the line of fire, in the distance A O (fig. 149), will be inversely proportional to the squares of the initial veloci- ties. 456 DIFFERENT KINDS OF FIEES. Fig. 149. If we suppose the lines of fire of two projectiles be A C^and A C, and the initial velocities, T^and V, to be such that they will fall the distances B C'and B' Q\ and that the angles subtended by these lines be propor- tional to the lines themselves, we shall have B A C: B' AC':: V" : V\ It has been seen that the initial velocities of small charges are nearly proportional to the square roots of the weight of the charges. Calling the corresponding charges O and C, we have B AO : B' AC •.-.O- -.C, or, for the sarm distance of the object, the charges should he inversely proportional to the difference between tlu^ angle of fire and angle of elevation of the object. Take the case in which the objects are situated at different distances, as B and B" (fig. 149), but have the same angle of elevation e ; and suppose we wish to strike them with the same angle of fire ; what should be the relation between the charges ? Substitute in the expression \g-&, the value of t, which is — , in which D is the distance, and V the initial ve- locity of the projectile, we have \g-^rj^-, which shows that the distance which a projectile falls below the line of fire is directly proportional to the square of the dis- tance measured on the line of fire, and inversely pro- PRACTICAL EULES FOR RICOCHET FIRE. 457 portional to the square of the velocity. But the dis- tances B " G" and B C are proportional to A O" and A C, or D" and Z>, and, recollecting that the squares of the initial velocities are proportional to the charges Cand C'\ 'we have D":B: B' ■ 0' or, B" -.B:: 0" : C, or, for the same difference hetween tlie angle of fvre and the angle of elevation of the object, the charges are pro- portional to the distances. In arriving at the foregoing rules, we have committed three errors: 1st. Supposing the sides of the triangles proportional to the angles. 2d. Considering the re- sistance of the air nothing; and, 3d. That the initial velocities are proportional to the square roots of the charges. The errors resulting from these suppositions are not only small in themselves, but the 2d and 3d are of a nature to counteract each other. By means of the foregoing relations suitable charges can be calculated for every case of practice, vrhen we know the charge corresponding to a given distance, and to a given difference between the angle of fire and the angle of elevation of the object. Represent by C the charge corresponding to a distance, B', and to a diifer- ence, E', between the angle of fire and the angle of ele- vation of the object; we have the charge, 6' corre- sponding to the distance, Z>, and the difference, E, be- tween the two angles, by means of the formula ^_B C E' ^~E B"" 458 DIFFERENT KINDS OF FIRES. C IE' The factor, — -^ is a constant number for each- cali- bre. This number may be considered as the charge corresponding to the distance of 1 yard, and to a differ- ence of 1° between the angle of fire and of elevation of the object. For the French 8-inch siege howitzer, the value of this factor has been found by careful experiment to be 0.31 oz. Making an allowance for difference of weight of projectile and unit of distance, it becomes 0.28 oz. for the American 8-inch siege howitzer. Exam-pie. — Find the angle of arrival, angle of fire, and charge of powder, necessar}' to hit, with an 8-inch howitzer shell, a point on a terreplein, 12 yards behind a traverse which is 2.5 yards high and 350 yards from the battery — the angle of elevation of the crest being 1°, and the command 6 yards. For the angle of arrival we have BC '^=''°AB- 60° X 2.5 12 = 12° 30'. For the angle of fire we have 0=« + 2e=12°3O'-f2°= = 14° 30'. For the charg e we have ^ D C=-=^0.28oz.= Ml 350- „„„ =Y.25 oz. 449. Rolling Are. Rolling fire is a particular case of ricochet fire, produced by placing the axis of the piece parallel, or nearly so, with the ground. It is generally used in field service. When the ground is favorable for ricochet, the projectile, in rolling fire, has a very long range, and never passes at a greater distance above the ground than the muzzle of the piece; it is therefore more effective than direct fire, as may be seen by in- specting fig. 150. EFFECT OE EIEE IK GENEBAI,. 459 Kg. 150. To point a piece in rolling fire, dvrect it at the object^ and depress the natural line of sight so as to pierce the surface of the ground about 80 yards in front of the ■lauzzle; if the piece be sighted for the pendulum hansse, aim directly at the object with tlie lowest line of sight, or with the slider fixed at the zero point of the ■scale. 450. PUinsiiig flre. A fire is said to be plunging when the object is situated below the piece. This fire is par- ticularly effective against the decks of vessels. 451. Effect of flre in general. Before proceeding to describe the fires of different kinds of projectiles, it may l)e proper to explain what is meant by accuracy of fire, and to determine a suitable measure for it. It has been seen that there are causes constantly at work to deviate nearly every projectile from its true path. As the effect of these deviating forces cannot be accurately foretold, there is only a probability that the projectile will strike the object against which the piece is pointed. The de- gi'ee of probability is called accuracy of fire. For all projectiles of the same nature, the chance of hitting an object increases with the velocity and weight of the projectile, whereby the effects of the deviating forces are diminished ; it also increases as the size of the object is equal to, or greater than, the mean deviations, and as the trajectory more nearly coincides with the line i)f sight. If the size of the object be greater than the e.Ktreme deviation, and the trajectory coincide with the 4G0 DIFFEBKNT KINDS OF FIRES. line of sight, the projectile ^vill be certain to hit the object at all distances. 452. McasMi-e of deviaSioji. For the same trajectoi'}-, therefore, the mean deviation of a projectile at a given distance may be taken as an indirect measure of its ac- curacy at this distance. To obtain this mean deviation, let the piece ]>e pointed at the centre of a target, stationed at the re- quired distance, and fired a certain number of times — say ten — and let the positions of the shot-holes, meas- ured in vertical and horizontal directions, be arranged in the following; tabular form : a 1 o 1 Distances from centve of target, in feet. Dist.inces from centre of impact, in fecL 1 Vertical. Horizontal. Vertical. Horizontal. Above. Below. Eight. Left. Above. Below. Eight. Left. ■ 1 2 3 3 1 4 2 2 4.33 .33 4.66 2.66 .66 3.33 3 i 1 2 4.C6 4.66 3.33 3.33 i 4-^-3 = 1.33 1 4-^3 = 1.33 1 1 9.32 -^ 3 = 3.1ll6.66 -^3 = 2.22 The algebraic sum of the distances in each direction, divided by the number of shots, gives the position of the centre of impact in this direction. In the above table the position of the centre of impact is found to 1 >e 1.33 ft. below, and 1.33 ft. to the right, of the centre of the target. To obtain the mean deviation, it is necessary to refer each shot-hole to the centre of impact as a new origin of co-ordinates ; and this is done l)y subtracting the tabular distance from the distance of the centre of impact, if both be on the same side of the DEVIATIONS. 461 centre of the target, and adding them, if on different sides. The ^um of all the distances thus obtained in one direction, divided by the number of shots, gives i he mean deviation in that direction ; which in the present case is 3.11 ft. vertically, and 2.22 horizontally. The foregoing affords a measure for the accuracy of fire of the piece and projectile, but it does not afford a measure for marksmanship, the object of which is to di- rect a j)rojectile so as to strike a given point or surface. In target-practice with sporting rifles, the string^ or sum of the distances of a certain number of shots, from the point aimed at, is taken as the measure of accuracy. In military arms, marksmanship is measured by the greatest number of projectiles out of a certain number, l)laced in a target of given size, or placed within a given space surrounding the centre of the target. 453. Targets. Targets for heavy cannon are made of cotton cloth (or light boards) stretched over two upright poles firmly secured in the ground. The size varies with the distance : for 1,000 yards and upward, it should be about 20 feet high and 40 feet long. Targets for the field service are made of the same matei'ial^, about 8 feet high, and from 30 to 40 feet long. Targets for small arms, if permanent, are made of cast-iron ; if portable, of a wrought-iron frame cov- ered vs^ith cotton cloth. For distances less than 200 yards, they should be 6 feet high and 22 inches broad ; beyond this distance, the breadth of a target may be i ncreased by placing two or more of these targets side by side. 454. Bsjviatiffliis. The vertical deviation of a pro- jectile is generally greater than its corresponding hori- 462 DIFFEEEKT KINDS OF FIRES. zpntal deviation, and this difference increases Avitli the range. As objects against Avhich military projectiles are directed, present a greater extent of surface in v. horizontal than in a vertical direction, it becomes ne- cessary to exercise great care in the selection of the proper angle of fire. If the ground or water in front of the object be favorable to ricochet, the difficulty will be diminished by aiming so that the projectile will strike the object after one or more rebounds. 455. Solid-shot firing. Solid shot are generally used for percussion and penetration, and, when heated to a red heat, for the purpose of setting fire to wooden vessels or buildings. From their great strength, they can be fired with a large charge of powder, Avhich gives them great initial velocity, and having great density, which diminishes the effect of the resistance of the air, they have great range and accuracy. lu firing hot shot, the charge should be reduced, to pre- vent too great penetration, which would exclude the air and render combustion impossible. The extreme range of field artillery is about 3,000 yards; it is not very effective, however, beyond 1,700 yards for the 6-pdr., and 2,100 yards for the 12-pdr. At 600 yards the horizontal deviation of the 12-pdr. is about 3 feet, and at 1,200 yards it is about 12 feet. For the 6-pdr. the deviations are somewhat greater at both distances. The service of solid shot demands less skill than that of shells and spherical case-shot, and they are often effective when the latter are rendered non-effect- ive by untimely explosion. 456. Shell-Hring. The diameter and velocity of two SHELL-FIEING. 46^^ projectiles being the same, the retarding eifect of the air is inversely proportional to their weight (see page 406) ; hence a shell has less accuracy and range than a solid shot of the same size, in the proportion of 3 to 2 — these numbers representing the weights of a solid shot and shell, respectively. Field sliellij. As shells act both by percussion and explosion, they are particularly effective against ani- mate objects, earthworks, buildings, block-houses and shipping, posts and villages occupied by troops, and against troops sheltered by accidents of the ground ; but against good masonry they have but little effect, as they break on striking. Against troops, especially cavalry, they possess a certain moral effect Avhich polid shot do not possess. They are used to form breaches in intrenchments, in which case they act as small miues. The 32-pdr. shell is the most effective field projectile for this purpose ; and, when fired Avith a • large charge, has a penetration of from 5 to 8 feet in fresh earth. The extreme range of field shells is from 2,500 to 3,000 yards. The 24 and 32-pdr. shells burst into about eighteen effective fragments, some of which are thrown to a distance of GOO yards. All field shells have considerable lateral deviation; it is stated that the 24-pdr. shell is sometimes deviated as much as 30 yards in 1,200. Mountain shells. The extreme range of the moun- tain, howitzer is about 1,200 yards, after three or four rebounds. The 12-pdr. shell emj)loyed in this service bursts into twelve or fifteen fragments, some of which are thrown to a distance of 300 yards. 464 DIFFERENT KINDS OF FIEES. Siege shells. The great weight of an 8-incli shell, and tlie large quantity of powder which it contains, render it a very formidable projectile against the traverses and epaulements of siege Avorks. Seorcoast shells. In sea-coast defence, the 8, 10, and lo-inch shells are very destructive to vessels built of tim- ber. They range from 3 to 3* miles; but the angle which the trajectory makes with the line of sight at this distance (about 40°) renders their fire very uncertain against individual objects of the size of a ship ; but it is ])resumed that they would have the effect to jorevent a blockading fleet from lying at anchor Avithin their range, as it is well known that a single 10-inch shell, striking on the deck of a vessel, has sufficient force to penetrate to the bottom and sink her. The 8-inch shell bursts into 28 or 30 fragments; and from the experiments made at Brest, some years ago, it was inferred that three of four of these shells, j^roperly timed and directed, were capable of disabling a ship of war. Mortar shells are employed to break through the roofs of magazines, roducing the same effect as the howitzer. Shells act by percussion, by explosion, and by moral effect ; and they should be employed in preference to shot under the following circumstances, viz. : 1st. When the enemy is stationary and under cover. 2d. When the ground is much broken, or cannot be seen. 3d. When troops are posted in woods. 4th. From one mountain to another. 5th. When the enemy is posted on higher or lower ground. 6th. When on a road leading through a valley. 7th. For incendiary purposes. 8th. In pursuit. 9th. Whenever it is necessary to produce a moral rather than a physical effect. EMPLOYMENT OF SIEGE-CANNON. In siege operations, the same fires are employed as in the field, but under different circumstances. The position of the object is generally fixed and known, and there is sufficient time to consider the best means of attaining it. 475. liong ranges. The greatest range of the 24-pdr. 494 EMPLOYMENT OF FIELD-AKTILLERY. siege-gun, mounted on its appropriate carriage, is about 3,500 yards; but the defence sliould not, without gooct reason, make use of a greater distance than 950 yards, or point-blank distance, for it is his duty to economize his ammunition, if it cannot be replaced. It will be proper to fire at a reconnoitring party at a distance of 1,000 or 1,100 yards, to prevent a nearer approach, and against strong attacking columns, provided they offer sufficient surface to render the chances of hitting probable. In the attach Firing at long ranges, on the part of the besiegers, should be strictly forbidden, as it would disclose to the enemy the proposed front of attack, without any compensating advantage. In the siege service, it is more important to avoid useless firing than in the field, for every shot that does not contribute to the progress of the attack, by weaken- ing the defence, is a shot lost. 476. Enfilading amu counter fires. An enfilading fire is directed along a particular portion of a work, and a counter fire is directed toward it. In the defence. Solid shot are used in enfilading and counter fires under the following circumstances : 1st. To destroy the head of a sap, or the parapet of a trench. 2d. When the enemy passes from the first to the second parallel, and before he has completed the bat- teries intended to dismount the artillery of the garrison. 3d. To batter vigorously the lateral works of attack as soon as they are finished. 4th. To protect and support sorties. The guns placed on the parapet of the place keep up a warm fire of ENFILADING AND COUNTER FIRES. 495 solid sliot against the batteries of attack, and tlic; lieads of saps, until tlley are masked by the troops making the sortie. 5th. To prevent the enemy from following too closely upon the heels of the party, which, having made the sortie, are returning, successful or otherwise. 6th. From the guns placed on the flanks of the bas- tions Avhen the besiegers attempt to pass the ditch ; in this case the fire is plunging. 7th. To drive the besiegers from any outwork that they may have taken. 8th. In a cannonade, the object of which is to dis^- mount the besiegers' guns. In thiS attack. The object of enfilading fire in the attack of a place, is to rake the terrepleins of the facea^ curtains, &c., and to render them untenable ; for this pui'pose the batteries should be established on the prolongation of, and at right angles, or nearly so, with the direction of the part to be enfiladed. As the ^ox- tion of the works to be attained is not commanded by the besiegers' cannon, enfilading fire, under these cir- cumstances, becomes ricochet fire, the nature and treat- ment of which have already been described. Enfilading and counter batteries are generally es- tablished at 300 or 600 yards from the place, or at the first and second parallels. As the object of a counter battery is to silence the fire of the place by dismount- ing the guns, its pieces should be directed against the embrasures. This demands great care in aiming, and great accuracy of fire ; the heaviest smooth-bored or rifled gims should therefore be employed for this purpose. 496 EMPLOYMENT OF EEELD-ARTILLEET. 477. Firing in breach. When tlie besiegers have approached to a suitable distance to commence the breach, the opposing artillery will have been silenced ; but they will be subjected to flank and rear fires, against ..which they will protect themselves by traverses. Counter-batteries will also be established with the breaching- batteries, the object of which will be to silence the artillery bearing on, the breaching-batteries, and the passage of the ditch. The method of forming a breach has already been described. 478. Fire of case-§liot. Case-shot should be employed in the defence of a work under the following circum- stances, viz. : 1st. In sorties, where field-artillery can be employed. 2d. At all points liable to sudden attacks, as on avenues leading toward gates, or on bridges. Pieces situated on the flanks are particularly suited to this fire. 3d. Against the gorge of an outwork which the enemy may make a bold attempt to seize. For this purpose, pieces on the curtains, or shoulder angles, should be employed, taking care, at the same time, not to fire over works occupied by the defence. 4th. This fire may be safely employed in the defence of dry ditches, reveted with masonry. 5th. Against the batteries of the first parallel during their erection, and after their position has been disclosed by means of fire-balls. 6th. Against the head of a sap at night. 7th. Against the workmen engaged on the construc- tion of the second parallel. 8th. Against the workmen engaged on the third par- FIEE OF THE SIEGE-HOWITZEE. 497 allel, against the -works leading to tlie covered way, and against the crowning of the covered way. 9-th. Against craters formed by the explosion of mines, to prevent the enemy from crowning them. 10th. Against the passage of the ditch. • 11th. Against the breach. 1 2th. All cannon on the flanks which remain mounted, fire rapidly grape or canister shot at the moment of assault. In the attack. The besiegers are much more restricted in the use of case-shot than the besiesred. It should be principally employed under the following circumstances, viz. : 1st. By cannon placed on the flanks of attack when- ever the besieged make a sortie, and come within suita- ble rann-e. 2d. At night, against the embi'asures which have been cannonaded during the day vsdth solid shot, to prevent them from being repaired. 3d. Against the flanks, during the night. 4th. Against the breach during the day or night, as soon as completed, to prevent the enemy from erecting means for defending it. 5th. Against the besieged, if he attempt to pass out through the breach, after the assault has been repelled. 479. Fire of the sieg^e-howitzer. The siege-howitzer should be employed in the defence, — 1st. Against an attacking column, when the gi'ound in front of the place affords a shelter against the fire of guns. 2d. Against the works of the besiegers. Howitzers 32 498 EMPLOTMEin' OF EIELD-AllTILLEBY. are placed on the salients to blow up, with shells, the works situated on the prolongations of the capitals. 3d. Against the batteries in process of construction on the three parallels. 4th. "Against the heads of saps ; this fire should be executed with small charges. 5th. The counter approaches are armed with how- itzers. 6th. Against troops opposing sorties, and especially against cavalry. 'Tth. Against the enemy's depots, when their position is known, and when they are within effective range. 8th. Against the enemy's convoys, when they can be reached, and they offer sufficient surface. In tlie attach. Howitzers are employed by besiegers — 1st. In a bombardment, by day and night. 2d. During all periods of the siege, when occasion requires. 3d. In the halfparallels established between the second and third; against the covered- ways and places of arms. The fire is executed with small charges. 4th. For ricochet fire, in preference to cannon. 480. iJse of firc-toasis. Fire-balls are used by the de- fence — 1st. Against columns of attack. 2d. Against the opening of parallels, so soon as it is ascertained that preparations are made for this purpose. 3d. Against points in the space occupied by the be- siegers, where a remarkable noise may be heard, and there is reason to suspect that it proceeds from pre])a rations for attack. 4th. Particularly when it is thought that the be- FIRE OF MOKTAE8. 499 ■; siegers are about to move forward fro;m one parallel to another. 5tli. To' discover the movements .of \h.e enemy after lie has repulsed a sortie, and to prevent him, by the jftre of the guns of the place, from following too closely in , pursuit. : 1)1 attach. As it is for the interest of the besiegers to ; conduct their operations as silently and unobserved as possible, they mil seldom have occasion to use fire-balls. 481. Fire of mortars. Mortars generally perform a more important part in siege operations than howitzers ; there are times, even, when they play a very decided part; too much care, therefore, cannot be employed, to render them effective. In the defence. Mortars are employed in the de- fence — 1st. Concurrently with howitzers, when the shape of the ground in front shelters the enemy from the fire of the guns. 2d. Against batteries and heads of saps. 3d. Against places sheltered from the fire of flanking guns. Mortars, and particularly light mortars, can be suitably placed at all points, and without interfering with the establishment of gun and howitzer batteries. 4th. Against the Avorks of the besiegers generally, and especially against the opening - of parallels, and the passage from one parallel to another. 5th. When the besiegers' fire has silenced the fire of the guns, the fire of the mortars continues in full activi- ty, not only in the body of the place,, but in the demi- lunes and lateral works. 0th. In covered batteries, during the entire siege, bajt 500 EMPLOYMENT OF FIELD-AETILLEEY. particularly during or after the construction of the third parallel. 7th. Light mortars should be employed in the coun- ter approaches. 8th. Against the workmen who are engaged in run- ning the sap up the glacis, for the purpose of crowning the covered way. 9th. To prevent the construction of counter and breaching batteries. 10th. To prevent the besiegers from establishing themselves in the craters formed by the mines. 11th. To drive the besiegers from any exterior work which they have taken. 12th. To prevent the passage of the ditch, or render it difficult. 13th. To prevent the besiegers from effecting a lodg- ment in the breach, by firing from the interior retrench- ment. In the attack. It is very difficult to specify all the cii'cumstances which should govern the besiegers in car- rying on a bombardment, since they depend on a variety of causes ; the following, however, may be enumerated : 1st. In a regular attack, mortars are the first to open fire, which should be kept up night and day vrhenever a result can be obtained. 2d. Heavy, and sometimes medium-sized, mortars, can be employed to retard the enemy's works on the front of attack, the armament of his batteries, the transporta- tion of his cannon, and to shower shells upon the places where his troops assemble, and to burn his principal buildings, etc. Light mortars are rarely used for these jmrposes, in consequence of the distance of the object MOKTAll CASE-SHOT. 501 and the liglitness of the shells, Avhich have little force of percussion. 3d. Mortars are employed to throw shells over the entire surface of the ramparts of the front of attack; and, for this purpose, the fire should be taken in the direction of their length. 4th. They are also employed against the lateral works as soon as the enemy seeks to establish his guns there for the purpose of retarding the works of attack. 5th. The curved or mortar fire of the second parallel is as efficient as that of the first parallel, at all periods of the siege. Light mortars here begin to. be usefully employed. 6th. Light mortars are also used with great advan,- tage in the half-parallels. From this period of the siege, the covered- way and places of arms, are showered with shells. Yth. From the. period of the third parallel, the ene- my's flanks are plied with mortar shells, to support the fire of the counter batteries. 8th. As soon as the cpvered-way is crowned, and sub- sequently, when a lodgment in the breach shall have been effected, Coehorn mortars are employed against the enemy, who has withdrawn to the interior retrench- ment of the bastion. 482. Mortar' case-shot, &c. Stones and case-shot from mortars, should be thrown by the defence as soon as the besiegers pass to the construction of the third parallel, and the batteries pertaining to it. This should be con- tinued during the crowning of the covered-way, and during the assault. The besiegers, on the contrary, employ these projec- 502 EirPLOYMENT OF SEA-COAST AKTILLERY. tiles in all the batteries of the third parallel, and, by this means, seek to drive the enemy from the covered way and places of arms, thus preparing the way for the assault. SEA-COAST DEFENSES. 483. Nature Of defenses. The means employed for the defense of harbors, are : 1st. Artillery mounted on fortifications, floating batteries, monitors and ships of war. 2d. Channel obstructions, such as rafts, heavy . chains, and surikea vessels. 3d. Torpedoes and torpedo ; vessels, both of which act under water. These means • may be used singly, but the most effective defense is made by combining them, according to circumstances. ' The introduction of steam into vessels of war, and their protection by armor plates have necessitated con-., siderable change in the construction of sea-coast forts and their armament. The best temporary fortifications.; are made of earth, with large masses in the way para-i, pets, traverses, etc., for covering the guns. It is now proposed to secure a still better covering for the guns by mounting them in iron turrets, similar in shape and con- 1 struction to the Monitor turrets, but to be manoeuvred; by man instead of steam power. Late experiments- show that the plan of reveting the masonry of case- mated works with wrought-iron plates will not answer, as the iron affords but little protection to the masonry. Monitors as a means of harbor defense have the advan- tage of being able to select their position of attack and , of following an attacking vessel if it should succeed in , passing the guns of a fort. The range and accuracy of AKMAIIENT OF SEA-COAST BATTERIES. fjOIJ guns mounted on Aoating defences are not so great as those of guns mounted on fortifications, and tliey are liable to be destroyed by rams. Ohstructiovs. The object of obstructions is to detain attacking vessels under the fire of the guns of the foits and monitors. They may consist of i-afts of strong timbers, oi- heavy chains sustained by buoys, or rows of piles, with suitable arrangements to let in or out friendly vessels. Sunken vessels should only be em- ployed when there is very little commerce to be intei- fered with, or when it is not practicable to employ other means. Ropes and netting may be placed in a channel to foul the propellors of hostile vessels. Torpedoes. Torpedoes and torpedo vessels were used in the late war in a great variety of forms and with some success. Torpedoes may be made of boxes or bar- rels covered with pitch, but the largest are made ot boiler plate riveted together. They are exploded by contact, by electricity, by clock-work or by time-fuzes. 484. Arnianicnt. The armament of sea-coast batteries depends on their importance and on the depth and width of the channel to be defended. Deep channels which peimit the entrance of large vessels and wide channels requiring long ranges should be defended with guns of heavy calibre. The salients and flanks which generally have an enfilading fire on a channel, should be armed with the heaviest rifle-cannon. The curtains and faces which bear directly upon it may be armed with heavy smootb-bored cannon. In addition to the cannon enumerated on page 192 as properly belonging to sea-coast armament, each fort should be provided with a certain number of field-. 50-1 EUPLOYJIENT OF SEA-COAST ARTILLERY. pieces, principally howitzers, to pi'event a landing, or to act in close engagements against the rigging and small boats of vessels. Forts shonlil be provided with fur- naces for heating shot which have been found to be effective in protracted engagements with wooden vessels. 485. Fires. Direct, ricochet, and plunging fires are piincipally employed in sea-coast defence. Direct fire should be used when the surface of the water is rough, and the accuracy of the rebound cannot be depended upon. The accuracy of sea-coast fire is generally greater than that of the field or siege service, for the reasons, that, the distance of the object, though moving, can be readily and accurately determined by its relation to known objects, the effect of shot can be more easily observed on water than on land, and the size of the object is large, and its appearance, generally, well defined. In aiming at a vessel with direct fire, the piece should be pointed at the water-line ; for, if the pro- jectile strike the water, it will either penetrate the hull below the water-line, or rebound and strike above it. The range of effective direct fire does not much ex- ceed one mile and a quarter ; the extreme range of sea- coast mortars is about two and a half miles ; that of the columbiads, about three and a quarter miles, and the heavy rifle-guns about five miles. The accuracy of ricochet-fire depends on the surface of the water ; itinder favorable circumstances, the larger sea-coast shells have a range of about 3,000 yards in rolling fire; their penetrating force, however, is very much diminished toward the extremity of this range. The fire of mortars, from ship-board, is very uncer- tain, if the surface of the water be much disturbed. TABLE ONE, 505 CHAPTEE Xin. TABLES OF MULTIPLIERS. B, I, I), V, &c. 48Y. Explanation. It woulcl exceed the limits of tMs work to enter into a discussion of tHe formulas from wliicli the values of the multipliers used in the equa- tions of motion in air (page 412) are calculated; it will be sufficient to explain how these tables are used in practice. The pupil will find this subject, as well as all others relating to Ballistics, ably and fiiUy treated in Didion's Traite de JBalistique. 488. TabJe 1. Multiplier B. The decimals are car- ried out to three places, which is sufficient for ordinary '7' • purposes. The values of — are given in the first hori- zontal line, the value of — '- in the first vertical col- r umn, and the values of the corresponding multipliers are set opposite to them. To find the multiplier B for two inteimediate values of — and — '-. not given in the tables, we seek, in the r absence of the proper numbers, the corresponding values of the nearest tabular numbers. We add to these, parts proportional to the differences, as though each part were to be considered separately. 506 TABLES OF MTJLTIPLIEES. X V Example. — Find the value of £ for _=0.5755, and — '=1.1219, c r i. e. B (0.5765; 1.1219). Starting witli 0.55 in tho first liorizontal column, and 1.10 in the first vertical column, we find ^=1.479; the difference between this and the next number of the horizontal line is 0.054 ; the difierence between the same and the next number of the vertical column is 0.013. The difference between 0.5755 and 0.55 is 0.0255, and between 1.1219 and 1.10 is 0.0219. The value of B (0.5755; 1.1219)=1.479+2:^^0.054 +^:^Voi3 = 1.479 + ^ ' 0.05 0.05 0.027 + 0.006 = 1.512. Or, for greater convenience, the foregoing may be placed in the fol- lowing form, the differences being written as whole numbers : _B (0.5755; 1.1219)— 1.512 _B(0.55; 1.10) =1.479 255 5-00^^ • • = 27 219 13 . . — 6 ,500 Multiplier^ I. The values of /are given in the same table as those of JB; except that it is necessary to com- mence in the lower horizontal line, and subtract from Y / V\ them the product of— 'M-] ^j, by the corresponding number of the line called " correction." Example. — To find the value of / (0.5755; 1.1219), take 5= c 0.545, which is less than the proposed number by 0.305, and which differs by 0.035 from the next number in the table; — '=1.10isthe r nearest number to 1.1219 in the first vertical column; for these two numbers we have 7=1.771. This number differs from the adjoining horizontal and vertical numbers in the table by 0.066 and 0.022 re- spectively. The value sought is 1.830, as is thus shown: TABLE FOUK. 507' / {0.6755; 1.1219)^ 1.830 / (0.545; 1.10) =l.'7'ri 305 -i506« = S8 219 22 = 10 600 —1.1219.2.1219.4= —9 Table 3. Vcihies of JI and B. TMs table is calcula- ted for differences of 0.10 in case of -» in tlie upper line, G V, ... I, . and for differences of .05 in case of — '-. For JJ. tHe T ' values of - are found in the upper horizontal line, and for Z>, in the lower line. Example.— YvcL^ the values of (7(0.6755; 1.1219) and D (0.5755; 1.1319). , ,, CT (0.5755; 1.1219) = !. 707 U (0.50; 1.10) = 1.597 755 loooi^^ = -10^ 219 We have ^= 1.707, and Z> = 1.336. D (0.5755; 1.1219)=1.336 D (0.393; 110) = i.221 1825 J^119 = .113 219 500^ = -OO^ -Table 4. Values of -Bfor the calculation of Ranges. ' QG CD r^ This table gives the value of -^ for values of - and — '^ & ^ or for differences of 0.05 and 0.05 ; the unknown quantity to be determined is -when — and -±i=p, are ariven. Arrange the calculations as in the preceding cases. Only one of the proportional parts is unknown, and this is determined by the condition, that if it be added to' the other proportional part, and to the number in tlje table, the sum is equal ,to the required number. 508 TABLES OF MULTIPLIERS. V X X Examples. — Having -f =1.1219 and -B, or ^—0.8729, find -. F Starting witli —- = 1.10, and following the horizontal line, we coiiio upon 0.8135, the nearest approach to the proposed number, 0.8729. Find X .r the corresponding value of —, which is 0.55.; the unknown value of — surpasses 0.55 by a certain quantity which we shall call A ; following the previous arrangement of the calculation, and observing that the differences of 0.8135 with' the adjacent horizontal and vertical tabular numbers are 0.1065 and 0.0071, respectively, and representing by 2' the result, we have — p{0.55 + ^; 1.1219)=0.8720 p (0.55 ; 1.10 ) = 0.8135 A 777^-1065 = .0559 0.05 0.0219 ' o-:o5ro^^ =-°°35 559 We have A=-— —0.05 =0.0263 1065 -=0.55 + 0.0263 =0.5763 c The proportional part 559 is equal to 8729 — (8135 + 85). TcAle 5. Values of r for initial velocities. 7e This table gives the quotient arising from dividing Y X V —'■ by \/B for values of - and — ' ; the quantity to be Y determined is — ^. The method is the same as in the r preceding table ; if the value of the quotient q dimin- ishes as - increases, the sign of the difference should be G changed. Example. — Having - =0.6755, and(y = >• = 0.9110, find Yj. TABLES. 509 X The vertical column nearest to —=0.5755 is that which corresponds to 0.55 ; the number in this column nearest to 0.9110 is 0.9045, which corresponds to 1.10, and the diflFerence between this and the required number is 0.0065 ; the differences with the neighboring numbers to the right and above, arc — 0.0162 and 0.0370, respectively. We therefore have, g- (0.5755; 1.10+A) = 0.9110 2'(0.55; 1. 255 162 500 10) = 0.9045 = — .0082 ^ 370 0.05 = .0147 A "7 "'■^=370 0.05 = 0.0199 Y and ^^=1.10+0.0199=1.1199 r The proportional part 147 is equal to 9110 — (9045 — 82), giving V A =0.0199, which, added to 1.10 gives — = 1.1199. 510 TABLES. Table 1. — Values of B and /. r fC 1 0.00 0.05 0.10 0.15 20 0.25 0.30 0.85 0.40 0.45 O.iJO . r U.HO 0.05 ,0.10 U.15 (1.21) 1.000 1.000 1.000 1.000 l.UOU 1.017 1.018 1 .019 l.OiO 1 .020 1.084 1.0.36 1.08- 1.039 1.041 1.0.52 1.055 1.067 1.060 1.063 1.070 1.074 1.077 1.081 1 .085 1.089 1.09< 1.098 1.108 1.107 I.IOS 1.114 1.119 1.126 1.180 1 .Vi8 1.184 1 141 1.148 1.1.'4 1.14'* 1 .1,56 1.163 1.171 1 r9 1.169 i.i;t 1.1-6 1.195 1 205 1.190, 1.200 1.210 1.220 1.281. o!25 0.80 0.8i 0.40 0.4D 0.50 0.55 0,61) 1 000 1 021 1.043 1 .065 I.O58 1.112 1.136 1.161 1.187 1.21' 1.241 ilooo 1.000 1.(100 1.000 1.000 l.flOO 1 .022 1.0-28 1.024 1.025 1.'025 1 026 1.045 1.046 1.048 1.00 1.02 1 .0.53 1.06S 1.071 1.073 1.076 1.0:9 1.082 1.092 1.096 1.099 1.103 1.107 1.110 1.117 1.121 1.126 1.181 1.135 1.140 1.142 1.148 1.1.-3 1.159 1.165 1.171 1.168 1.176 1.182 1.189 1.196 1.203 1.195 1.203 1.21' 1.219 1.227 1.235 1 .223 1.2 2 1.241 1 25' 1.260 1.269 tl.262 1.273 1 .283 1.294 1.305 ^,"1 1.000 1.027 l.O.-iS 1 084 1.114 1.145 1.176 1.209 1.244 1.29 1.815 1.826 «!■■-• 0.10 0.75 1 .000 1 028 1 0.57 1 C87 1.118 1.149 1.182 1.216 1 .26/ 1.238 S 1 1 JlOO 1 029 1.069 1.090 1.122 1.154 1.188 1.224 1 260 l.iHS 1.337 o i!ono 1.030 1.060 1.092 1 .'125 1.1.59 1.194 1 281 1.26S 1.30S 1.843 1.359 fe HO 1.000 1.081 1.062 1 096 1.129 1.164 1.200 1.238 1.277 1 .317 1 0^85 90 1 . (100 1 031 1 .06+ 1.098 1.133 1.169 1.206 1 .v45 1.286 1.827 1 .370 I'ooo l!08i 1.066 1.101 1.187 1:173 1.212 1.262 1.94 1.337 1.382 0.95 1 .00 1 .000 1 .033 1 067 1.103 1.140 1.178 1.21> 1.269 1.802 l.M 1 .398 1.000 l!034 1.069 1.106 1.144 1.188 1.224 1.266 1 810 1.856 1.404 1 0.) 1.000 1 085 1.071 1.109 1.148 1.188 1.230 1.278 1.319 1 .806 1.416 1 'l.( 1 000 1 . 086 1.073 1.112 1.151 1.193 1.280 1.2S1 1 32S 1.376 1.427 1.15 1 000 1.037 1.P75 1..114 i;i65 1.198 1.242 1.288 1.-336 1 SS6 1.438 121 1.000 1.087 1.070 1.117 1.159 1.203 1.248 1.295 1.34, 1.396 1 .450 1I25 1.000 1.088 1.078 1.120 1.168 1.207 1.254 1.808 1.353 1.406 1.461 X c 0.000 0.038 0.007 0.101 0.134 0.1C8 0.202 0.236 0.270 O.804 0.533 Correcti .n....| 0.000 0.000 0.000 O.OW) 0..000 ' 0.000 "0.000 0.001 0.001 0.001 0.001 For B X O.EO 0.55 0.60 0.65 0.70 0.75 O.SO 0.86 0.90 0.95 1.00 0.00 1.190 1.212 1.284 1.257 1 .2.31 1.305 1.330 1.366 1.882 1.409 1.4<7 005 1.200 1.2-23 1.247 1.271 1.296 1 .822 1.848 1.875 1.40 1.43' 1.461 o!io 1.2IO 1.284 1.259 1.285 1.811 1.8.39 1.366 1 .395 1 .4'.'5: 1 .4f>B 1.480 0.15 1 .220 1.246 1.272 1 .-m 1 ,,327 1.356 1.385 1.415 1 .4471 1 .479 1.512 o!20 1 231 1 .2i5S 1.286 1.814 1.848 1 .873 1.404 1.486 1.469 1.603 l,5i^ D 25 1.241 1.269 1 .298 1.828 1.369 1 ..390 1.428 1.467 1.491 1.5'!7 1.66S 0.30 1.252 1.281 1.311 I..343 1.376 1.408 1.442 1.477 1.514 1.651 1 ,590 0.85 1 .262 1.293 1 .8/5 1.857 1.891 1.425 1.461 1.499 1 .,6«6 1.5:6 1.616 0.40 1.278 1.30C 1.338 1.872 1 .407 1.443 1.48' 1.520 1.659 1.601 1.648 0.45 1.2S3 1.817 1.351 1.8-7 1.428 1.461 1.600 1.541 1.588 1.626 1.670 0.50 1.294 1.829 1.805 1.402 1.440 1.479 1.620 1.668 1.'06 1.661 1.697 ^ *- 0.55 1.805 1.34 1.378 1.417 1 .457 1.498 1.540 1.584 1 630 1.6i7 1.725 0.60 1.815 1 .8.5C 1.892 1.482 1 .473 1.616 1.560 l.tiOb 1.664 1.70' l.i58 Lfl 0.9( 1.483 1.47a 1 .5-t4 1.572 1.022 1.674 1.7i7 1.7vi 1.8.39 0.80 1.S69 1.40.' 1.447 1.494 1.542 1.691 1.648 1.696 1.761 1.809 1.86S 0.S5 1.370 1.41. 1.462 1.50S 1.655 1.610 1.664 1.719 1.776 1.^86 1.897 ilO 1.3S 1.42 1.47r 1.52t 1.577 1.0,30 1.6-B 1.743 1.802 1.86- 1.927 95 I 898 1.4401 1.49( 1.541 1.694 1.649 1.706 1.76b 1.8/7 1.891 1 .957 1 .(to 1 .404 1 .4:^1 1 .504 1.6.5? I.61S 1.669 1.728 1.7S9 1.858 1.919 1.9^7 I .05 1.-I15 1.41i(i. 1.5 a 1.67- 1.63( 1.6SS 1.749 1.813 1 .879 1.947 2.017 1 .10 I 42" I.4TO1 1 .5 f 1..69( 1.64' 1.70S 1.771 1.887 1 .90,'' 1.97S 2.048 1 .15 i.' 1.S61 1.981! 2.0Q4 2 079 1 .20 1 .4.5(1 1 505 I.IJO."- 1.02Mi 1.68' 1 1.749 1.81« 1 .8.86 1.968 2.0.33 2.111 1.-.5 1.461 1.51.^ 1 .57J 1.689; 1.70 i 1.769 1.S3S 1.910 1.S8E 2.O61 2.142 For / 1 tJ 0.S3- 0.872 40 1 0.441; 0.47 5 O.iil 0.54! 0.5SC O.6I; 0.669 0.6S3 Corri'C 1 ion ... 0.00 0.00 2 0.00 , 0.00 !j 0.00 ) O.OOS 0.004 t 0.004 0.00. > O.OOE 0.006 TABLES. 511 Values of B and / — {Continued^ 512 TABLES. Table 3. — Values of V for velocities and D for times. U 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 0.00 1.000 1.051 1.105 1.162 1.221 1.284 1.860 1.419 1.492 1.568 1.649 0.05 1 .000 1.0B4 1.110 1.170 1.233 1.298 1.367 1.440 1.516 ■1 597 1.681 0.10 1.000 1.056 1.116 1.178 1.244 1.812 1.885 1.461 1.64] 1.626 1.714 0.15 1.000 1.069 1.121 1.181 1.255 l.t-27 1.402 1.482 1.566 1.654 1.746 0.20 1.000 1.062 1.126 1.1H4 1.2 6 1..341 1.420 1.503 1.590 1.682 1.779 0.25 1.000 1.004 1.182 1.202 1.277 1.865 1.487 1 624 1.615 1.710 1.811 0.30 1.000 1.067 1.1S7 1.210 ].2Ss 1.S69 1.455 1 546 1.189 1.7S9 1.843 0.o6 1.000 1.069 1.142 1.219 1.2s)9 1.383 1.472 1.666 1.664 1.707 1.876 0.40 1.000 1.072 1.147 1.227 1.310 1..19S 1.490 l.,58. 1.689 1.79ri 1.908 0.45 1.000 1.074 1.158 1.235 1.821 1.4)2 1.607 1.603 1.713 1.824 1.941 0.60 1.000 1.077 1.158 1.248 1.332 1 .426 1.525 1.629 1.738 1.868 1.978 ^^ s- 0.55 1.000 1.080 1.163 1.251 1..34S 1.440 1.542 1.050 1.72 I.SSII 2.006 a 0.60 1,000 1.082 1.168 1.269 1.354 1.454 1.5>i0 1.'71 1.7S7 1.909 2.0:^8 u 0.65 1.000 1.035 1.174 1.267 1.866 1.469 1.577 1.6 2 1.S12 1.'33 2.070 tg 0.70 1.000 1.0S7 1.179 1.275 1.376 1.483 1.695 1.712 1.S36 1.966 2.103 0.75 1.000 1.0^0 1.184 1.283 1.388 1.497 1.612 1.7-18 1.S61 1.995 2.135 0.80 1.000 1.092 1.189 1.291 1.399 1.511 l.CTO 1.754 1 .885 2.023 2.163 0.85 1.000 1.095 1.195 1.299 1.410 1.525 1.647 1.775 I.'IO 2.0.51 2.200 0.90 1.000 1.097 1.200 l.SOS 1.421 1.540 1.065 1.796 7.9.35 2. 080 2.28:J 0.95 1.000 1.100 1.205 1.P16 1.432 1.564 1.6S2 1.817 1.9.59 2.103 2.265 1.00 1.000 1.103 1.210 1.824 1.443 1.563 1.700 l.'8S 1.984 2.137 2.297 1.05 1.000 1.105 1.216 1.332 1.464 1.6S2 1.717 1.P69 2.003 2.105 2.:-.30 1.10 1.000 1.108 1.221 1.340 1.466 1.597 1 .736 1.S80 2.083 2.194 2.862 1.15 1.000 1.110 1.226 1.348 1.476 1.011 1.752 1.901 2.067 2.222 2.895 1.20 1.000 1.118 1.281 1.356 1.487 1.025 1.770 1.922 2.082 2.2.50 2.427 1.25 1.000 1.115 1.237 1.864 1.498 1.629 1.787 1.943 2.107 2.279 2.460 For 1) X c 0.000 0.198 0.393 0.535 0.775 0.962 1.14G 1.827 1.606 1.6&3 1.858 For as a 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 0.00 1.649 1.733 1.822 1.916 2.014 2.117 2.226 2.840 2 460| 2. .556 2.71S 0.05 1.681 1.770 1.863 1.961 2.064 2.173 2.287 2.407 2.538 2 665 2.304 0.10 1.714 1.807 1.904 2.007 2.115 2.229 2 343 2.474 2.606; 2.744 2 S90 0.15 1-.746 1.848 1.945 2.053 2.166 2.286 2.409 2.541 2.679 2,824 2.976 0.20 1.779 1.880 1.987 2.099 2.217 2.840 2.471 2.608 2.7621 2.9(13 8.06'i 0.25 1.811 1.917 2.028 2.144 2.267 2.896 2 532 2.675 2.825 2 9,S3 8.148 O.-O 1.S43 1.9.53 2.069 2.190 2.313 2.452 2.693 2 742 2 898 3.1101 3.234 0..35 l.t>70 1.990 2.110 2.286 2.869 2.503 2.656 2.i-09 2 971 3, 141' 8.320 0.40 1.90S 2.027 2.151 2. 282 2.419 2.664 2 716 2.876 8.043 ;5.22l) 8.406 0.45 1.941 2,063 2.192 2,328 2.470 2.620 2.777 2 943 8.116 8.299 3.492 ^ 0.50 1 .973 2.100 2.2.33 2.873 2 5il 2.676 2.838 8.010 3.1.S9 3.379, 3.,577 — ^ 0.55 2.006 2.137 2.274 2.419 2.571 2.731 2.900 3.077 3. ana s.j.xs 3,663 c ■ 0.60 2.03S 2.173 2.315 2.465 2.622 2.787 2.961 8.143 8.8.36 3.537 3.749 f^ 65 2.070 2.210 2.857 2.611 2.678 2.S43 8:022 3.210 8.408 3,010 3, .'85 ^ 0.70 2.101 2 247 2.393 2.666 2.723 2.899 8. 088 3.2:7 3.431 3.006 8 921 0.75 2.135 2.2S3 2.439 2.602 2.-;74 2,965 8.145 3.844 8.. 554 3 77.->' 4.007 0.80 2. 168 2.320 2.4811 2.043 2,825 8.011 8.206 8.411 8.627 S,S."4' 4,098 0.85 2.i00 2.857 2.521 2.694 2.875 3.066 3.267 8.478 3,700 8,9:>? 4,179 0.90 2.238 2.893 2.. 562 2.740 2.926 3.122 3.829 8 545 3,773 4 013 4.265 0.95 2.265 2.480 2.608 2.7S5 2.977 8.178 8.390 8 612 3.846; 4,09-2 4.351 ■1.00 2.297 2.467 2.644 2.831 3.028 8.2.34 8.451 8.679 8.919 4,171! 4.487 1.05 2.8S0 2.508 2. 685 2.877 8.073 3.290 X.612 3.746 8.r.92! 4.2.il 4.523 1.10 2. .362 2.540 2.736 2.923 8.129 8.346 8.874 8.818 4.0651 4.3301 4.608 1.15 2.895 2,577 2.768 2.963 8.1M 8.402 8.6.35 8,630 4 1 8' 4,4119; 4.694 1.20 2.427 2.618 2.809 8.014 8.230 8.457 8.696 8. 947 4.21li 4.4-9 4.730 1.25 2.460 2.660I 2.S50 3.060 8.281 8.513 8. 763 4.014 4.2S4J 4..'iOS; 4.86« F«r a l.SoS 2.030 2.199 2.3C9 2.685 2.701 2.864 1 3.026 8.186 3.844 3.501 TABLES. 513 X- Table 4. — Values of -B for ranges, 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.S5 0.40 0.45 0.50 0.55 O.CO 0.05 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 0.00 0.05 0.000 0.000 0.000 0, o.ooolo 0.0000, 0.0000, 0.0000, o.ooo!o, 0.000,0, 0.0000, 0.000 0, 0.000 0, 0.000 0, 0.000 0. 0.0000. 0. 000,0, o.oooio. 0.000 0. o.oooio. 0.000 0. o.oooo. 0.0000, o.oooo. 0.000 0, 0,000 0. 0.0000. 0.10 ,0508 ,050910 0509 !0 0610!0 0510 0511:0, 05Il|0, 0511.0, 0512 0512 0, 0518 0, 0513,0, 0614 05140, 05140, 0515:0, 0515 0, 0516 0, 0516 0, 0517,0. 0517 0, 0517 0, 0518 0. 0518 0, 0519 0. 0519,0, 0.15 ,1084 ,1036 ,1033:0 ,1089:0 ,104110 ,104S'0 ,10450 ,1046;0 10480 10500 1053 10530 1056: 1057 0, 1059 1060 0, 10620, 10640, 1066 0, 106710, 10690 1071 1078|0, 1075,0 10760, 1078,0, 0.20 ,1578 ,1582 ,1586,0 ,1590i0 ,1594 ,1598,0 ,1602!o ,1606;0 ,i6io;o ,1014,0, ,1618 0, ,162210 ,162610, 163010, ,16340, ,1638!o, 1643:o ,164710, 1651 0, 1655l0, 1669'0, 16680, 1667:0, 1671 jO, 16760, 1680 0, ,2140 ,2148 ,2155 ,2162 ,2169 ,2177 ,2184 ,2191 ,2199 ,2206 ,2213 2221 2228 2236 2248 2250 2258 2265 2273 2295 2808 2310 2318 0.25 2722 2734 2745 2757 2768 2780 2791 2808 2815 ,2850 ,2802 ,2874 ,2686 ,2897 2909 2921 2988 2946 2968 2970 2982 2994 8006 8019 ,8324 .8841 !o ,8357|0 ,8874i0 ,3891 !o ,840810 S426|0 ,84480 ,84600 ,8477:0, ,3494:0 851210 8529 0, 364710, S564l0 868210, 8600:0, 8017'0 0, 3653 3671 3707 3725 3761 ,8947 8970 ,3993l0 ,4017|0 .4040 ,40640 ,408810 ,4112 ,4186,0 ,4160,0 41840 4209,0 ,4288,0 4257 4282,0 4307j0 43320, 48560, 4881 ;0, 4407 0, 44320, 4457|0, 4482 0, 4508 0, 4.533 0, 4559 '0, 4591 0.! 4622 0.1 4654.0.1 ,4685 ,4716 ,4748 ,4780 ,4812 ,48440 .4877 ,4909lO ,4942l0 ,4974:0 ,6007:0 ,50-10;0 ,50740 51070 51400 5174:0 6208 !o 524210 5276,0 5810 ;0 63440 5379 6414:0 5879 5420 5461 5508 .6644 5686 5628 6070 .5712 6756 5797 5841 5884 5927 6971 6015 6059 6103 6147 6192 6237 6282 0.50 0.5949 0.6000 0.6051 0.C102 0.6164 0.6206 0.6268 0.6810 0.686S 0.6410 0.6470 0.6528 0.6577 0.6682 0.6686 0.6741 0.6790 0.6652 0.6908 O.6064 0.7020 0.7076 0.7133 0.7191 0.7248 0.7300 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.95 I 1.00 I 0.00 0.05 0.10 0.16 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.65 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 0.6949 0.60000 0.6061 0.6102 0.61.54 0, 0.6206 0, 0.6268 0, 0.6810 0, 0.6863 0.6416 0, 0.64700, 0,6623 0, 0.6577 0, 0.6632 0. 0.6686 0. 0.6741 lO, 0.6796 0. 0.6853 0. 0.6908 0, 0.6964 0. 0.7020 0. 0.7076 0, 0.7183 0, 0.7191 0. 0.7248 0, 0.73060, 6664 ,6727 ,678910 685210 69160 6981 7045,0 7110j0 7I75I0 72410 .7404 7807 7874 7441 7609 7577 7645 7714 7783 7852 7922:0 7993 lo 80640 8185!0 8206 '0 8278,0, 8350]0 + .7480 7556 7633 7711 7789 .7868 .7947 .8027 8107 8188 8269 8851 8434 8517 8600 8854 8940 9026 9118 9200 9289 ,9877 ,9466 ,81710 ,8262 0, ,8853 ,8445 ,86330, 8632,0, 8726 0, 8823 0, 8917,0, 9014 0. 9111 il. 9209 1, 93071. 9407,1. 9507.1. 9608 1. 970911. 981111. 99141. 0018 1 , 0122 1. 02361. 03311. 0489,1. 0546 1. 06541. 8964 0, 9072 0, 9I8OI1 9290 9400 9511 9623 9786 9850 9964 0080 0196 0818 0481 0651 0671 0792 0914'l 10861 1159;l 128411 1409 1 1536,1 1668 1 1791 '1 1920,1 9786 9912 00.39 0107 0296 0427 0658 0691 0824 0969 1095 1232 1370 1510 1650 1791 1988 2077 2222 2868 2615 2663 2812 .0784 .0981 .1080 .1230 .1882 ,1635 ,1690 ,1846 ,2002 ,2161 ,2821 ,2482 ,2646 ,2809 .2974 ,3141 ,8309 ,8821 ,8995 ,4170 ,4846 ,4524 ,4702 1521:1 1689 1 1860,1 2031 ll 2205'1 2380 1 2568,1 27371 2917:l 3099 1 3382 1 346711 36541 3858 1 1 4034I1 42251 4419 1 4614 1 4811,1 5009 ;i 531011 641111 5615,1 581911 60371 ,63361 1 2638:1 38281 8O20I1 321911 34201 3622,1 3838:1 40351 4348,1 44561 4667 ;1 4882:1,6176 6100 1 6819!l .3384:1. 4S65 3603 1 1.461 3 8826 1 .4864 .4050il.6n8 .427611.6376 .4.';06,1.5681 ,4786!l,6896 4970:1.6103 5207,1.6430 .64451.6701 .5686:1 .6974 6539 5768 .6424 6674 .6927 7188 1.7580 6215 6444 66751 6909:1 714411 .7882 1 1 .786111 1.7818 1.8098 i.fsse 1.8676 744011.8970 7700:1.9267 7964ll.9566 8229 1.9868 8495,2.0173 .876413.0481 9037 2.0792 9812 2.1105 9588,2.1422 33 514 TABLES. V. Table 5. — ^Values of r for initial velocities. c 0.00 0.05 0,10 0-15 0.20 0,25 0.30 0,35 0,40 0.45 0,60 lo. 0, 0. 0. 0. 0. 0, 0, 0. 0. 05 0000 .04956 ,04913 ,04869 .04825 .04782 .04788 ,04695 ,04651 .04608 .04564 10 O.OOOO' .09908 .09816:, 09725 .09634 .09543 .09432 .09362 ,09271 .09181 .'■9091 0.15 1 OOOO! .14857 ,14713 .14569 .14426 .14284 .14143 ,14001 ,13860 .13719 .13778 0.20 0.0000 .19800 .19601 -19402 ,19304 .191107 .18811 ,18614 .18418 .18233 .18028 25 O.OOOO .24789 .24480 ,24331 ,23968 .23708 .28434 .23200 ,22945 .22692 ,22440 0.30 0000 .296T6 .29361 ,29029 ,28710 ,28392 .28075 .27759 ,27444 .27130 -26818 0.35 0.00000.8461 0.3422 0.3383 0.3344 0.8.306 0.3267 ".3329 0,8191 0,3153 0-8116 0.40 0.00000.3953 0.3907 0.38610.8315 0.3770 0.8735 0.3680 0,8635 It, 3590 (1,8546 0.45 0.0000!0.4446 0.4-392 0.43381 ".4385 0.4232 0.4180 0.4128 0.4073 0.4024 0.3973 50 0.0000 0.4938 ).4S76 0.4815! 0.4754 0,4693 0.4633 0,4573 ".4513 0.4454 0.4896 u~ ^ 55 0.0000 0.5429 0.5339 0.5289(0.6220 0,5153 0.5084 0,5016 0.4948 0.4881 0.4815 c. 0.60 0.0000 0.6920 0.3S41 0.5762;0.56S5 0,561)8 0,5582 0,5466 1.5380 0.5805 0.5331 %4 0.65 0.00000.6411 ). 6333 0.6235 0. 6143 0,6063 0,5978 0,5894 ".5810 11.5727 0.5645 O 0.70 0. 00000. 6901 0.6S03 0.6706 0.6610 0,6516 0.6432 '1,6329 0.6236 0.6144 0.6058 0,75 0.0000!0.7891 ). 7283, 0.7176; 0.7071 0.6967 0.6864 0,6761 0.6659 ".6558 0.6459 0.80 0.0000 0.7880 0.7763|ii. 7645 0.75.311 0.7416 0.7303 0,7191 0.7080 0,6971 0.6862 85 O.OOOO'O.SSTO 0.82410.8113 0.7987 0.7868 0.7741 '1,7619 '.7498 0,7879 0.7261 0.90 O.OOOO! 0.8357 0.8717,0.8379 0.8448 0.8309:0.8176 0,8044 0.7913 0.7784 0.7657 0.95 0.0000 0.9347 0.9195,0.9045 0.8897 0.9871'0. 95091". 9849 0.8753 '0.8609 11.8467 0.8327 0.8188 0.8051 i.oa O.OOOO 0.9834 0.9194l0.9"40 0.8887 0.8736 0.8587 0.8489 1.05 0.03001.0332 1.0145 0.9971 0.9801 0.963410.9469 0.9305 0.9143 '.8984 0.8826 1.10 0.00001.0809 1.06201.0434 1.0231 1.0072 0.9895 0.9720 0.9547 0.9377 0.9210 1.15 0. 00001.1295 1.1094 1.0896 1.0700il.ii50S|l. 03211 1.0184 0.9949 0.9768 0.9690 1.20 0.00001.1781 1.1566 1.1-354 1,1146 1,0942 1.0741 1.0543 1.0348 1.0166 0.9967 1.25 0.00001.2267 1.2038 1,1813 1, 1593, l,1875ll, 1162 III! 1.1'952 1.0745 1.0541 1.1-841 ^ 0.50 0.65 0,60 0.65 0,70 0.75 0.80 0.35 O.90 0.95 1,00 I lo. 0. 0, 0. 0. 0. 0. 0. 0. 0. 0. 0.05 .04564 .04521 ,04478 .04435 ,04892 .04849 .04806 .04263 .04221 .04178 ,04136 0.10 .09091 .09001 ,08911 .08821 .03782 .08644 .08565 .08466 .08378 .08289 .08202 0.13 .13778 .13438 .13299 .13160 .18 21 .13883 .13746 .12608 .12471 .12334 .12193 0.20 .18 23 .17835 .17648 .17461 .17259 .17069 .16830 .16691 .16503 .16816 .16128 0.25 .22440 .23190 .21942 .21694 .214481,21203 .2(1958 .20715 .20473 .20233 .19994 0.30 .26818 .26507 .26198 .25390 .2.3583: .25285 .24988 .24682 .34383 .24087 .23798 ■ 0.35 11.8116 0.3078 0.3041 0.3 04 0.2963 0.2932 0.2895 0.2859 0.2834 0.2788 0.2758 0.40 11.3546 0.35 '2 0.3433 ,1.3415 0.8373 0.333" 0.3387 0.8245 0.8208O.S162 0.8121 0.45 ".8973'0.3923 0.3871 0.3821 ".3772, '.8733 ".3674 0.8625 0.35770.8529 0.8483 ^ . 0.51) 0.4.396 0.4333 0.4280 0.4328 0.4167,0.4111 0.4065 0.4000 11.3945 0.8891 0.8888 ^*^\ ^ 0.55 0,4815:11.4750 0.4833 11.4621 0.4567,0.4494 0.4482 0.4870 0.4808lo.4247 0.4187 a 1 0.60 0.53.310.5158 0.5086 0.5014 ".4943 0.4873 0.4804 0.47-35 0.400610.4598 0.4581 b 0.65 0.5645 0.5563 0.64S3 11.5403 0.5335 0,5347 0.6170 0.5093 0.3018,0.4944 0-4870 ^ O.TO 11.6053 0.5964 0.5875:0.5788 ',57' 2 0,6616 0.5.333 0.5448 0.5305,0.5284 0.B203 0.75 0.6459 0.0361 0.62640.6169 0,6"73 0.,39S1 ".5389 0.5798 ■.B7llS:0.5619 0.55-31 0.811 0.6862 0.S755 0.6630l0.6546 '1.6443 0.6343 0.0242 0.6143 0.60450.5949 0.6W>1 0.85 0.7261,0.7145 0.7031 0.6919 0.6808 6698 0.6689 0.6482 0.63770.6273 0.6171 O.ftO 0.7657 0.7582 '1.7409 0.7288 7168(1.7 50 0.6934 0.6819 0.670611.6594 0.6484 0.-.5 0.81151 '.791610. 7783 0.7652 0.7534 0.7-398 0,7273 11.7149 o.7028l0.6909 0.6792 l.iiO 0.B489 0,8295,0,8153 0.8014 ", 7870:", 7741 0,7608 ■1.7476 0.7S41|0.7219 0.7094 1.05 0.8836 '1.86710,852(1 0,8871 0,8225 0,8081 0,7939 0.7798 0.76600.7523 0.7893 1.10 0,921' 0.9046'0.8883 ,0.872f 0,857010,8417 0,8265 '.8116 0.7970 '0.7827 0.7686 1.15 0.9590 0.9415:0,9243 ".9 75, ".8900 0.8747 0,8688 0.8480 0.8273:0.8124 0.7975 1.211 0.9967 0, 978110, 9599jO,9421|0. 9246 0.9076 0,8906 0.8789 0.85760 8416 0.8260 , 1,25 1.0841 1,01450.9953,0.9764 0.9579 0,9898 0,9220 0,9045 0.8873.0.8705 0.8540 TABLE FOB BALLISTIC MACHINE. 515 r Table of Times, calculated for the West Point Ballistic Machine. Length of simple pendulum, 5.769 in. ; and 2nl 360^2^? =0.001509" Time of Time of Degrees. passage for Sum of Times. Degrees. passage for Sum of Times. each degree. each degree. 1 .00151 2B .00159 .08987 2 .00151 .00302 27 .0(1159 , .04140 3 .00151 .00453 28 .00160 .04306 4 .00151 .00604 29 .00161 , .04467 5 .00151 .00755 30 .00162 .04629 ;6 .00151 .00906 81 .00163 .04792 |V .00161 .01057 32 .00163 .04955 's .00151 .01208 33 .00164 .05119 9 .00151 .01359 34 ,00165 .05284 10 .00152 .01511 35 .00166 .05450 11 .00152 .01663 36 .00167 .05617 12 .00152 .01815 37 .00168 .05785 ,13 .00152 .01967 38 .00170 .05955 '14 .00163 .02120 39 .00171 .06126 15 .00153 .02273 40 .00172 .06298 16 .00163 .02426 41 .00173 .06471 17 .00154 ,02580 . 42 .00175 .06646 18 .00154 .02734 43 .00176 .06822 19 .00155 .02889 44 .00178 .07000 20 .00155 .03044 45 .00179 .07179 21 .00156 .03200 46 .00181 .07360 22 .00156 .03366 47 .00182 .07542 23 .0015'? .03513 48 .00184 .07726 24 .00157 .03670 49 .00186 .07912 25 .00158 .03828 50 .00188 .08100 Example. — What is the velocity of a projectile when the time of its passage between two targets, 100 feet apart, corresponds to 20.5 degrees of the graduated arc 1 Time of 20° — 0.03044 Log. of 100 = 2.000000 Add for 0.5° 0.00077 Log. 0.06242 = 2.795324 Time of 20°. 5: 0.03121 2 Log. 1602. = 3.204676 Double arc - = 0.06242 Velocity = 1602. feet. TABLES OF FIRE. With the exception of those for mortars, the following tables of fire were calculated by Bvt. Brig.-Geu'l J. A. Haskin, TJ. S. Artillery, by aid of the equations of the movement of projectiles in air given in Chapter VIII., and 80 far as they have been verified they agree remarkably well with those obtained in practice. The " range" is understood to be the distance in yards at which the projectile first strikes the horizontal plane drawn through the centre of the muzzle of the piece. When the object is situated below this plane the angle of elevation of the piece, if measured by the quadrant, should be corrected by the table on page 532. In aiming at the object direct, with the breech-sight, no correction for the elevation of the piece is considered necessary, if the angle of elevation or depression of the object does not exceed 15°. The weight of each projectile, the value (c), and the initial velocity (I. V.), are given in the tables in each case. RANGES. 511 Kind of Ordnance. Charge. Projectile. Elevation Range. Time. Remarks. / Yards. Seconds 6 Pdr. Field Lbs. Shot. .30 298 c Gun. 1.25 I 5°7 Wr.— 6. 1 5 lbs. 1 • 3° 670 c.=a66o - 804 I.V.=i44o 2 3 3 4 5 6 7 8 9 10 • 3° • 3° 918 1018 1 106 1184 1323 1442 1546 1638 1721 1796 .30 328 •77 1.25 Spherical. I 537 1.44 Case. I 30 697 827 2.07 2.65 Wt.— s.slbs. 3 30 936 1030 3.18 3.68 c.=2379 3 30 1112 4^'7 I. V.=.S5o 4 5 6 7 1186 1315 1425 1521 4.62 6.36 7.14 •15 .30 181 Ranges oTjlaincd' 11 Pdr. Field ^•S Shot. 320 at Washington Gun. Wt.=i2.3lbs. I •45 452 562 Arsenal, March, 1^66. ^.=3338 1 '5 662 ° / Yiirds I.V.=i486 1 I 30 45 75° 832 906 1. 609 1. 30 760 2 30 1040 2. 876 3 1158 2. 30 1C60 3 30 1261 3. 1185 4 1355 3.30 1280 5 1521 4. 1360 6 1663 6. 1620 7 1788 g 1899 9 1999 10 2090 •3° 324 ■77 2-5 Spherical I 554 1-45 Case. I 30 733 882 2.09 2.65 Wt.=ii.25 ■J. 30 1010 3--5 3.8 3 1 1 20 «.=3053 3 30 1218 4^3 I. V.=i4.9s 4 5 6 7 1307 1462 1595 1711 4.81 5^73 6.62 7.46 ^ 8 9 10 1815 1907 1992 8.27 9.05 9.82 518 RANGES. Kind of Ordnance. charge. Projectile. ilevation. Range. Time. Remarks. / Yards. seconds i2Pdr. Field Lbs. Shell. •3° 367 .82 Gun. ■-'•5 I. 59° 1.52 Wt.=9 lbs. 1.30 765 2.18 (•.=2442 2. 2.30 900 1014 2.78 3.36 [.V.=i68o 3- 3.30 I112 "97 3.88 4.36 4- 5-' 6. 7- 8. 9- 10. II. 12. 1274 1408 1521 1619 1706 1784. 1855 1919 1979 4.84 5-75 6.57 7.42 8.19 8.92 9.64 10.34 11.98 .30 232 .64 izPdr. Field X. Shell. .1. 405 1.23 Howitzer. 1.30 - 545 1.78 Wt.=9 lbs. 2. 662 2.30 C.=2442 2.30 3- 763 850 2.77 3.26 I. V.=i239 3.3° 4. 5- 6. 7- 8. 930 1002 1127 1235 1329 1413 3.72 4.15 5- 5-79 6.54 7.26 9- 1488 7-95 10. 1556 8.61 .30 214 .61 1, Spherical i. ,385 1. 18 Case. 1.30 2. 529 6S3 1.72 2.24 Wt.= II.25 2.30 3- 763 859 2.73 3.21 5 roc Gun. lO. Wt.=99.5lbs. (;.=a0240 I.V.=-I222 3 4 5 6 7 8 9 lO '5 20 »s 3° 986 14.20 1824 2200 ^554 2888 3205 3506 3792 5062 6127 70C8 7906 I 486 1.27 lO, Shull. 2 3 937 1356 2.52 3-74 Wt.^ioi lbs. 4 •745 21 10 4-94 6.11 (;.=20545 2454 7.26 I V.=ii88 7 8 9 10 •5 20 25 30 2780 3089 3384 3664 4932 5918 6899 7740 8.4 9.52 10.63 11,72 17.28 22.i -7-55 3 3-° 3 I 599 lO. Shot. Wr — Ro lbs. c.=i6zTi I.V.=i33S 2 3 4 5 6 7 8 9 10 15 20 25 30 1126 '594 2015 2401 2752 3077 337S 3660 39-4 5032 583° 6416 6831 .3° 3^7 •74 8. Dyer Shell. I 1 627 30 900 1.46 2.17 VVt.=6i.5 2 "53 2.86 C.= 12$10.2 2 3 30 1388 1606 3-53 4.19 I.V.=i3S4 3 4 S 6 7 S 9 10 30 1810 2003 2359 26S2 2976 3^45 3494 3726 4.83 5-47 6.71 7.91 9.07 10.20 11.33 l^ 42 34 530 RANGES. The fallowing ranges are determined by practice, and lie in the plane of the platform on which the bed stands. Kind of Ordnance. 8 Inch Siege Mortar. (Model 1861.) 10 Inch Siege Mortar, Charge, lbs. oz. o. 8 0. 12 1. O I. 4 I. 8 1. 12 2. O Projectile. 8 Inch Siege Howitzer. As a Mortar, 0. 8 1. o 1. 8 2. O 2. 8 3- ° 3- 5 4- o Shell. Wt=46 lbs. Shell. Wt.=90 lbs. Elevation, Range, 45- 0. 12 1. O I. 4 Shell. Wt.=46 lbs. Yards. 360 703 1082 1412 1 741 1985 2225 Time. Seconds 8.0 12.5 15.0 17.0 18.S 20.0 21.0 Model 1861. iSg 245 854 1 1 22 1410 1676 1843 2064 3'4 620 1082 1440 1925 6.4 10.4 14.2 17.2 18.4 19.8 20.9 21.9 Remarks. Ranges obtain- ed from experi- ments made near Petersburgh, Va., by the jst Conn. Artillery, in Sept. 64. Old Model. Range. 123 276 522 774 "44 1466 1811 202S Time. 300 553 1332 169s 6.9 11.5 14.6 17-5 TABLES OF FIRE. 531 RANGES WITH SEA-COAST 1 3 INCH MORTARS, ac° ELEVATION. Charge. Mean time of Flight. Least Range. Greatest Range. Mean Range. Lbs. Seconds. Yards. Yards. Yards. 4 8 840 877 869 6 9-5 1209 »3'7 1263 S 11.66 1653 1840 «744 10 12.50 2010 2128 2066 12 14.25 2369 2688 2528 ^ 15.25 2664 2780 2722 RANGES WITH 13 INCH MORTARS, AT 45° ELEVATION. 1 3 Inch Mortar. Powder. Shell. Elevation. Range. Lbs. 20 Lbs. 200 45° Yards. 432.5 RANGES WITH 13 INCH MORTARS AT 45° ELEVATION. Charge. Flight. Fuze. Range. Lbs. oz. Seconds. Inches. loths. Yards. 7 21.4 4 ^1 2190 7 8 22.4 4 4 2346 8 23.2 4 6 2480 8 8 23.8 4 7J 2600" 9 24.4 4 8| 2734 9 8 24.9 4 9j 2853 10 25.4 5 I 2958 10 8 25.9 5 1 4* 3026 II 26.3 5 ^i 3'5° II 8 26.7 5 3i 3246 12 27.0 5 4 3327 12 8 27.4 5 4j 3404 •3 27.7 5 5^ 3470 13 8 28.0 5 6 355* '4 28.3 5 6J 3617 14 8 28.5 5 7 36S1 IS 29.0 5 8 3739 IS 8 29.1 5 8} 3797 16 29.2 5 Si 3849 16 8 29.4 S 8:} 3901 '7 29.6 5 9 3949 .7 8 29.8 s 9} 3997 18 29.8 5 9i 4040 18 8 30.0 6 4085 19 30.2 6 0^ 4123 19 8 30.3 6 o| 4160 20 30.5 6 I 4200 — . ()33 RANGES. Table showing the angles of depression of an object for diiferent distances and beights of a gun above the water. I HEIGHT. M I Foot. 2 Feet. 4 Feet. 8 Feet 16 Feet. 32 Feet 64 Feet 96 Feet. Yards. / / / / / / / , / aoo 5-7- ii.S ■23. 45.8 I 31.6 3 3-i 6 5-5 9 S.5 250 4.6 9.2 18.3 36.7 I 13.3 2 26.6 4 53- 7 '7-6 300 3.8 7.6 iS-3 30.6 I I.I 2 2.2 4 4- -6 5.4 35° 3-3 6.5 13.1 26,2 52.4 I 44-7 3 29.4 5 J3-5 400 2.9 5-7 11.4 22.9 45.8 I 31.6 3 3-2 4 34-S 450 ■■'•5 51 10.2 20.4 40.7 I 21.5 2 42.8 4 ,4- 500 2.3 4.6 9-1 , 18.3 36.7 I 13.3 2 26.6 3 39-7 55° 2.1 4-2 8.3 16.7 33-3 I 6.6 2 13-3 3 '9-8 600 '■9 3.8 7.6 •5-3 30.6 I I.I 2 2.2 3 3-3 450 1-7 3-5 7- 14. 1 28.2 56.4 I 52.8 2 49.1 700 1.6 3-3 6.5 13.. 26.2 ■52.4 ' 44-7 2 37. 75° '•5 3- 6.1 12.2 24.4 48.9 I 37.7 2 26.6 800 '■4 2.8 5-7 11.4 22.9 45-8 I 31.7 ' 17-4 850 1-3 2.7 5-4 10.8 21.6 43-1 I 26,3 2 9.4 '900 '•3 3-5 5-' 10.2 20.4 40.7 I 21.5 2 2.2 95° 1.2 2.4 4.8 9.6 19.3 38.6 I 17.2 I 55.8 1000 I.I ^•3 4.6 9.2 18.3 36.7 I 13.3 I so. 1 1 00 I. 2.1 4-2 8.3 16.7 33-3 I 6.7 I 40. 1200 •9 1.9 3-8 7.6 '5-3 30.6 I i.i I 31.7 1300 •9 1.8 3-5 7- 14.1 28.2 56.4 I 24.6 1400 .8 1.6 3-3 6.5 13. J 26.2 52.4 I 18,6 1500 .8 '•5 3- 6.1 12.2 24.4 48.9 I 13.3 1600 •7 1.4 , 2.9 5-7 11.4 22.9 45-8 I 8.7 1700 •7 '•3 2.7 5-4 10.8 21.6 43-1 I 4-7 1800 .6 '•3 ■■'•5 5-' 10.2 20.4 40.7 I I.I 1900 .6 1.2 2.4 4-8 9.6 19.3 38.6 57-9 2000 .6 1.2 . 2-3 4.6 9.2 18.3 36.7 55- 2100 •5 I.I 2.2 4-3 8.7 '7-5 34-9 5--4 2200 •5 I. ■^.1 4.2 8.4 16.7 33-3 5°- 2300 .5 I. ■J.. 4- 7-9 15.9 31.9 47.8 2400 •5 I. 1.9 3.8 7.6 15-3 30.6 45-8 2500 •4 •9 1.8 3.6 7-3 14.7 29.3 44- 3060 .4 .8 '•5 3- 6.1 12.2 24.4 36.7 3500 ' -3 •7 '■3 2.6 5-i 10.4 21. 31.4 4000 : -3 .6 I.I -•3 4.6 9.2 1S.3 27.5 45°° ; -3 •5 I. 2. 4-1 8.1 16.3 24.4 5600 . .2 ■5 •9 1.8 3-7 7-3 14-7 When the height of the piece above the water or horizontal plane is known, the angle of depression for dillcrent distances can be found by using the foregoing table. Find the angle for any height not given in the table, as follows : divide the given height into parts, which are found in the table, using the largest num- ber possible j and add the angles corresponding to those parts, for the required distance. Example; required the angle for distance 1000 yards and height 23 feet. 23 feet gives the parts 16. 4. 2. & i; ; the sum of the angles for these heights is i8.3'-|-4.6'+2,3'-^i.i'=26,3'. _ In ujing the quadrant, or giving the elevation from the horizontal plane of the piece, if the, piece is higher than the object fired at, the angle of depression should be deducted' from the "elevation" in the table of ranges. Example: the 10 inch Columbiad at 6° gives about 2000 yards range; if the piece is 32 ft. above the object the angle of depression is 18.3' and the quadrant should be set at 51° 41.7'. VELOCITIES. 53S Remaining velocities for Sea Coast Projectiles, calculated by Capt. Stockton, Or5 J165 919 ,1045 924 69s 1293 1118 865 1007 854 632 1251 1032 741 964 792 550 1177 948 643. 1154 1 1 10 1028 1125 1056 939 1115 1048 927 Feet. «34 ^39 : 437 i8s 335 571 155 ' 276 505 . 20/ 382 63s ; 193 346 568 249 468 753 236 408 65a 323 552 , 857' 46. 90. 172. 7S , 144 261 85 151 273 534 RANGES. RESULTS OF EXPERIMENTAL FIRING with 15-inch Columbiad, from barberte platform No. 120 of Fort Monroe, Va., made between Oct, 24th, 1865, and Nov. loth, 1865, to determine tile penetration of a Solid Siiot and Shell into a Sand target (well rammed) 30 feet thick, 15 feet high, and fifteen feet front, 'located 400 yards from the Gun. to A •? 3 <^ >M ^-t .s i 4> Remarks. Q u . ,*& i 1 fe s 2 »- « u c; E c Q. J5 w ^ u S! Q !i p! a. Lbs. -/ Ft. In. Ft. In. Ft. In. I 5° 30 6 5 2 15 8 Solid Shot. Z' (C 15 5 ° 2 6 10 6 " " Struck ground before enter- 3 10 S 4 8 20 '* ** ing target. 4 15 7 4 8 16 (C (( S re 15 6 17 " " " Carriage struck c-heurter of Chassis and rebounded 3 t « 15 S '° 10 14 3 Shell. inches. » (t 30 58} I 6 II a % (( 30 6 2 7 10 u 4 <( 30 T8 7 6 9 8 n 5 « 30 3 10 10 15 " Chassis rails sanded. 1 45 15 7 4 8 18 Solid Shot. z (( 15 10 19 " « Carriage struck c-hcurter of 3 « 8 67 10 18 " '• Chassis and rebounded ij 4 M 15 7 15 " " inch. Carriage struck c- S K 15 6 10 7 16 " " hcurter of Chassis and re- £ U 15 6 6 6 12 " " bounded ij inches. f (C 30 S 6 6 9 Shell. z (C 30 4 4 3 8 ti 3 (( 30 5 • 7 9 " ti 4 c< 30 4 6 6 7 (( 5 (( 30 48 7 12 i< 6 (t 30 4 6 3 7 « i' 40 23 5 ° 6 11 Solid Shot. Struck ground before enter- 2 C( 8 6 3 4 12 « " ing target. 3 u 8 6 2j 4 12 6 tc (t 4 :** 8 6 II 6 17 it C( I -CI ' 8 5 " S 70 " " Same as above. £ « .8 S 1° 5 ° 12 (( it I " 30 2 9 3 6 Shell, Chassis rails sanded. Struck 1 .^- z^: a'-i^'r:':--.^:':': ■ Fig. 156 (a). Diagram A shows the position of the button in the deep part of the groove when entering the bore. C shows the manner of shunt- ing it to the shallow side ; a is the point at which the inclined plane commences. J} shows the button on the driving or shallow sid&. 2. ^''iiitVFortii gun. The Whitworth guns are made of a substance called " homogeneous iron," a species of low steel, which is said to be made by melting short bars of Swedish iron and add ■ ing a small quantity of carbonaceous matter, after which it is casf into round ingots. The smaller Whitworth guns are forged solid ; the larger are built up with coils or hoops, after the manner shown in fig. 157. In the Armstrong guns the coils are shrunk on by the aid of heat ; in the Whitworth guns the hoops are forced on by hydraulic * The Fraser, or " Woolwich guns," It is said, are rifled on the French but ton system as modified by Captain Palliser. The twist of tlie grooves is increasing with a view to diminish the strain on the breech of the gun, and to increase the accuracy 9f fire. "WHITWOItTH GUN. 545 Fig, 157. pressure, and for this jjurpose they are made with a slight taper and with the design to secure initial tension. The ends of the hoops arc joined by screw-threads. The hoops are first cast hollow and then hammered out over a steel mandrel, or rolled out in a machine like (.hat used for forming wheel-tire. Before receiving their final finish, Ihey are subject to an annealing process for some three or foui weeks, which makes the metal very ductile, but, at the satiie time slightly impairs its tenacity. The breech-pin is made with ofiseis in such a way as to screw into the end of the barrel and the next two surrounding hoops. The breech in the case of the large guns is hooped with a liarder and higher steel than that used for the barrel. Tiio 70 -pdr. gun has onelioop; the 120-pdr. proposed by Mr. Wiiitworth was to have lour tiers of hoops. The cross-section of the bore of the Whitworth guns is a hexatrou with rounded corners. The twist is very rapid, and the projectiles are made very long. Dimensions, dbc.^ of Whitworth Guns. Wsight III Projectile t20-pounder TO-poundor 13-pouncIer Diam. of JJoiP ncn)»* flats. Length. Weight. " Twist. Inches for one turn. Weii-'bt of Powder. Inches. Inches. Lba. h'm. 6.4 144 16,000 130 27 5. 118 8,583 100 IS. 2.75 104 1,093 53 1.7.5 Lhs 151 81 12 The proof consists in firing once with a service charge, with the powder increased one-fourth — and once with a service charge o powder and a si.\-calibre projeotiio, 3. Blak«ly gun. The moat ap])i-oved pattern of the Blakeix gun combines in its construction the principles of " initial teiisioi and " varying elasticity," the object of which is to bring the strongtl of all the metal of tlie piece into simultaneous play, to resist exi)it- sion. (See page 150.) 35 oU APPENDIX. Fig. 158 represents a 9-inch Blakely gun of this kind. Fig. 158. The inner tube, or barrel, is made of low steel, having consider- able but not quite enough elasticity. The next tube is made of high steel with less elasticity, and is shrunk on to the barrel with just sufficient tension to compensate for the insufficient difference of elasticity between the two tubes. The outer cast-iron jacket, to wliich tlie trunnions are attached, is the least elastic of all, and is put on with only the shrinkage attained by warming it over a fire. The steel tubes are east hollow and hammered over steel mandrels, under steam hammers ; by this process they are elongated about 130 per cent., .it the same time the tenacity of the metal is increased. All the steel parts are annealed. Captain Blakely uses other combinations of these metals, the sim- jilest of whicii is a cast-iron gun with hoops of steel surrounding the reinforce. He objects to the use of wrought-iron on account of its tenacity to stretch permanently. Blakely guns are rifled with one- sided grooves, and are fired with expanding projectiles. Dimensions, <&c., of Ulalcely All Steel Guns. Gun. Weight. lOO-pdr, ISO-pdr 200-pdr S.iO-pdr S50-pdr 350-pdr 700-pdr Lbs. 8,000 9,000 17,000 34,000 80,000 35,000 40,000 Diam. of Bore. Inches. 6.4 10. 11. 13. Length of Bore. Inches. 96 100 144 to 156 do. do. do. do. Number of Grooves. 13 13 15 13 13 Twist 1 turn in Calibres. 48 48 48 48 Weiaht of Projectile. Lbs. 100 130 200 350 350 550 700 Weiaht of Powder. Lbs. 10 13 30 25 35 55 70 PALLISER GUN". 547 4. PsUliscr gun. Captain Palliser, of the British service, de- scribes his manner of making a gun to consist in introducing into a cast-iron gun a barrel or hollow cylinder of coiled wrought-iron, of such thickness in proportion to its calibre, that the lesidual strain borne by the tube shall have a relation to the strain it transmits to the surrounding cast-iron, which shall be most suitably proportioned to their respective elasticities. The precise proportions will depend on various circumstances, viz.: the excessive expansion of wrought-iron due to lieat, also the greater range between the limits of elasticity and rupture of this inetal, and that the cast-iron will have to do nearly all the longitu- dinal work. By varying the thickness of the tube, the transmitted strains can be regulated with the greatest nicety. The mechanical method, says Captain Palliser, by which I pro- pose to insert the tube, is by making it very slightly taper, and placing it in the gun, the bore of which is tapered correspondingly ; as soon as the tube comes in contact with the gun throughout its length, a screw washer around the muzzle will screw it home into its place. See fig. 159 Fig. 159. Since the amount of taper, as well as the di.stance the tube is driven by the washer, is known, and the increment or decrement in cast or wrought-iron due to any pressure is also known, we shall in this manner be able to measure most accurately the strain placed on the cast-iron outer gun. In the larger guns Captain Palliser proposes. to use two or more concentric tubes. In the very largest guns he proposes three tubes, the inner one to be of the softest and most ductile wrought-iron ; the next may be of a stronger and harsher nature ; the third of steel for some distance in front of the chamber. Old smooth-bored guns have been reamed out and strengthened on Captain Palliser's plan, and have shown remarkable strength. The guns tested were chiefly 68-pounders. A 9-inch gun has lately 548 APPENDIX. been tested with severe charges, some as high as 45 pounds powder and 250 pounds projectile. 5. Parsons gun. The principle upon which Mr. Parsons makes his gun would seem to be similar to that of Captain Pal- liser's, i. e., by varying elasticity. As applied to strengthening a C8-pounder cast-iron gun, his method consists of boring into the breech of the gun, coincident with its axis, reaming out the bore into a slightly conical shape as far as the front of the trunnions, and then inserting into this space a reinforced wrought-iron tube, which is secured in its place by a breech-plug. The exterior of this com- pound tube is turned to fit the conical space easily, its length being cut so that it will be compressed longitudinally by screwing up the breech-plug, thus communicating to the outer cast-iron portion the entire longitudinal strain of the powder. Mr. Parsons bases his method on the fact, as stated by him, that wrought-iron may be stretched three times as much as cast-iron, and will offer from three and a half to six times the resistance within the limit of its elasticity. G. Krupp gmi. Mr. Krupp, of Prussia, makes his guns out of solid cast-steel of low quality. The steel is formed in crucibles in the usual way, and is then run into a large ingot, which consti- tutes the mass of the gun. This ingot is worked under jjowerful steam hammers, to give the requisite texture to the metal. In this way 9-inch muzzle-loading rifle cannon, weighing 16,800 pounds, have been made. The success of this manufacture is said to be owing to the very heavy machinery employed, the skillful heating of the large masses to the centre without burning the outside, and the presence of manganese in certain proportions in the iron from which the steel is made. v. Pai'i'oit g^iin. The Parrott rifle-gun is a cast-iron piece of about the usual dimensions, strengthened by shrinking a coiled band or barrel of wrought-iron over that portion of the reinforce which surrounds the charge. See fig. 160. Fig. 160. PARROTT GUM 549 The body of the larger Parrott guns are cast hollow, and cooled from the interior on the Rodman plan. The barrel is formed by bending a rectangular bar of wrought-iron spirally around a man- drel and then welding the mass together by hammering it in a strong cast-iron cylinder, or tube. In bending the bar, the outer tfide being more elongated than the inner one, is diminished in thick- ness, giving the cross section of the bar a wedge shape, which pos- sesses the advantage of allowing the cinder to escape through the opening, thereby securing a more perfect weld. The barrel is shrunk on by the aid of heat, and for this purpose the reinforce of the gun is carefully turned to a cylindrical shape, and about one-sixteenth of an inch to the foot larger than the inte- rior diameter of the barrel in a cold state. To prevent the cast- iron from expanding when the barrel is slipped on to its place, a stream of cold water is allowed to run through the bore. At the same time, and while the' band hangs loosely upon it, the body of the gun is rotated around its axis to render the cooling uniform over tlie whole surface of the barrel. Dimensions , dbc, of Parrott Guns. Gun. b O . 5^ 1" is = 2 1° It 11 fcij i i 5 1 Inches. Inches. Inches. Lbs. Indies. 1 tarn in ft. at Muzzle. Lbs. Lbs. lO-pdr.... 70 3. 11.3 890 3 ■ 0.1 10 1 10 20-pdr.... 79 3.67 14.5 1,750 5 0,1 10 3 19 30-pdr.... 130 4.20 18.3 4,300 7 0.1 13 3 28 100-pdr.... 130 6.4 35.9 0,700 9 0.1 18 10 86 8-incli. . . 13G 8. 33. 10,300 11 0.1 33 16 150 lO-inch... 144 10. 40. 36,500 15 0.1 30 25 350 The proof of the Parrott guns consists in firing each piece ten rounds with service charffes, *A large number of these guns were used in the late war, both on sea and land ; and the araount of work done by them, especial- ly in breacliing masonry, is (probably not exceeded by the rifle-guns of any other system. While a few of them have failed in the sei-- vice, others have shown very great endurance. The cause of this, * The number of Parrott guns procured by the War Department alone was upwards of 1,700, besides 3,000,000 of Parrott projectiles. 550 APPENDIX. failure has been attributed to the bursting of shells in the bore, the jMCsence of sand in the bore, etc., but late investigations show that the Parrott projectiles were frequently broken at the bottom by the force of the powder in such a manner as to wedge the body against the bore. It is quite probable that this cause Lad much to do with the bursting of the guns. The inventor thinks he has corrected this evil. 8. Brooke gun. The gun made after the plan of Captain Brooke, for the Confederate service, resembles Pari-ott's in shape and construction, except that the reinforcing band is made up of wronght-iron rings not welded together. In some cases two layers of rings are used. The rifling appears to be similar to that used in the Blakely guns. 9. Ames giiii. The rifle-guns of Mr. Horatio Ame?, of Falls Village, Coim., are made of wrought-i'ron on the built-up principle. Rings of a certain size are made by bending a bar of wrought-iron around a mandrel and welding it together at the ends. Two or more of these rings are carefully turned in a lathe, and fitted one within the other to form a disk. A number of these disks are welded together, two by two, commencing at the end of a bar of iron, which forms the breech of the gun, and is used for handling it in manufacture. The mass is then reamed out and turned to the proper shape. The trunnions are attached by being screwed into the body of the gun. It is understood that Mr. Ames now proposes to try the experiment of lining his guns with a steel tube. 10. Dalilgrreii gun. The Dahlgren guns of lai-ge calibre are made of cast-iron, solid, and cooled from the exterior. To produce uniformity in the cooling, the piece is cast nearly cylindrical, and then turned down to the required shape, which is shown in the an- nexed fi tical chamber of the Rodman system. Dimensions, die, of Dahlgren guns. Gun. Lcng:th (if Bore. Maxi- Tnum Diatii. Weight, Service Charge. Maxi- innin Cliarge. Weight ipf Shot. Weight or Slioll. 20 incli. , 15-incli. , 13-incli. 11-incli. . 10-incli.. 0-incli. 125-pdr . . Inch. 103 130 130 132 119J 107 1171 Inch. 64. 48. 44.7 32. 29.1 72.2 33.25 Lbs. 100,000 42,000 30,000 16,000 12,000 9,200 10,500 Lbs. 100 35 40 15 12i 10 40 Lbs. 60 20 10 13 Lbs. 1080 400 280 170 125 93 125 Lbs. 330 224 130 109 70 lOO 11. SSodmaii sjun. The principal difficulty formerly expe- rienced in manufacturing very lai-ge cast-iron cannon was the inju- rious Strains produced by cooling the casting from the exterior. As far back as the year 1844, General Rodman, of "the Ordnance Department, sought to discover the means to overcome this diffi- culty. After much observation and study, he developed his theory of the strains produced by cooling a casting like that of a cannon, and as a remedy for tbem he proposed that cannon should be cast on a hollow core, and cooled by a stream of water, or air, passing through it ; see page 136. After an elaborate series of experiments the truth of his theory was established, and his new mode of casting was adopted by the War Department. As a result of General Rod- man's theory, he claimed that he could cast cannon of any practica- ble size, and asked that a l5-incli cast-iron gun might be made. This was done in 1800, and the gun was successfully tested shortly afterwards. General Rodman then projected a 20-inch gun, which was made at the Fort Pitt foundry in 1863, under his dii-ections. n.'^Q APPENDIX Formeily it was customary to use but one kind or size of grain of powder for all cannon, whatever their size. General Rodman jiroposed for liis large cannon that there should be a proportional increase in the size of the grain, expecting tliei-eby to get as high a velocity for the piojectile without a corresponding increase in the strain on the breech or weak part of the piece ; this led to the in- troduction of our present Mammoth powder. Ho also thought that the powder which wonlJ produce the least strain on the gun, giving certain initial velocity to the projectile, would be that which should develop its gas as the space behind the projectile increased ; or in other words, that the powder should burn on an increasing instead of a decreasing surface. With this object in view he proponed to compress the substance of the powder into short hexagonal jn-isms, which could be easily fitted together without loss of space. These prisms were perforated with longitudinal holes, fi'om which the combustion of the powder spread. While this idea has to a certain extent been confirmed by experiment, this ])Owder has not been offi- cially adopted in this country; it is understood that it has been to a certxin extent in Russia for service in heavy rifle-guns. 'J'he trial, or No. 1 15-inch Army gun, has been fired 509 times with charges vai'ying from 3D to 50 lbs. of powder. The effect on the boie is hardly perceptible. The Navy 15-inch trial gun was fired 900 times with charges varying from 35 to 70 lbs., mostly Mortar or Navy cannon powder, when it burst. Within a short time another Army 15-inch gun has been firet. without injury 250 times, with charges varying from 40 to 100 lbs. of Mammoth powder ; one hundred of these were with 100 lbs. of powder and projectiles of 450 lbs. each. 15-inch gun No. 105 has likewise been fired as follows, viz. : No. times fired. . 4 Charge, CO lbs. Weight of projectile. 430 lbs. Initial velocity. 1191 ft. 3 7"0 lbs. 431 lbs. 12 78 ft. 3 80 lbs. 433 lbs. 1355 ft. 3 90 lbs. 453 lbs. 1433 ft. 2 100 lbs. 453 lbs. 1509 ft. Tlic Chief of Ordnance reports that 280 15-inch Rodman guns have been purchased for the use of the Army ; besides a largo num- ber liavo been procured for the Xavy, for use on the Monitors, RODMAN GUN. 553 where they rendered good sei'vice against the enemy's iron- clads and fortifications during the late war. Only, some two or three of the Navy 15-inch guns have split at the muzzle where they had been turned down very thin to fit the port-holes originally intended for the 13-inch Dahlgren gun. A 12-inch rifle-gun, having the exterior form and dimensions of the 15-inoli gun, lias been made and tested by firing it 420 times without injury, with charges of powder varying from 40 to 85 lbs., and projectiles varying from 475 to 620 lbs. ; an initial velocity of 1121 feet was obtained. Further experiments in large rifle-cannon are to be made at Fort Monroe, under the direction of the Chief of Oiduance. 20-i)u:h gun. The 20-inch gun made in 1863 has been thus far iired only eiglit times, a delay having been occasioned by a failure to get a suitable iron target against which to test its destructive l)Owers. Soon after it was mounted at Fort Hamilton, New York Harbor, it was fired four times with 50, 75, 100, and 125 lbs. of nianimotii powder, and solid shot weighing 1080 lbs. In March of this year (1867), it was again fired as follows : 1st fire, 125 lbs. powder, 25° elevation, 6144 yds. i-ange. 2d " 150 " " 25° " 6800 " " 3d 4th 175 " 200 " 25 = 6828 8001 The maximum pressure on the bore was 25,000 lbs. The form of the 15-inch and 20-inch Rodman gun is shown in fig. 46. Particulars and Charges of Hodman guns. Name of Gun. i Til Service Charge. ►3 ■ ^-. r^ f=o iSo Sinooth-Boies. Id. III. In. Lbs. Lbs. Lbs. Lbs. Lbs, 20-iu. gun. 343.5 310. 04. 115200 100 1080 lo-in. do. 190. 165. 48. 49100 (50 I ( mammoth. 17 ( 440 ) 1425 > 330 13-in. do. 177.0 155.94 41.6 83731 30 cannon. 7 ( 300 1 380 \ 324 10.iii.do.ofl860 130.G6 105.5 33. 15059 j 15 for shell.) i 18 for shot. ) 3 137 100 8-m. do. 123.5 110. 25.0 8465 10 1 68 4S 554 APPENDIX. 12. Oatlingr giin. The Gatling gun is a machine gun com- posed of six barrels made to revolve around a central axis paiallel to tlieir bores, by means of a hand-crank. As each barrel comes opposite to a certain point a self-primed metal case cartridge, fall- ing from a iiopper, is pushed into the breech by a plunger, and held there until it is exploded by the firing-pin. This gun is capable of firing as many as 200 shots a minute, with great range and precision. The machinery is simple, and little liable to get out of order. A number of these guns of 1-inch and |-inch calibre have lately been procured by the Government for use on the Plains, in flanking ditches, defending block-houses, etc. In addition to the solid ^ lb. bullet projected by the gun of 1-inch calibre, this piece fires a cartridge containing IG smaller projectiles, giving a very destructive fire for short distances. As the weight of this gun — about 1000 lbs. — is very great compared to that of the charge, the aim is not disturbed by recoil. 13. Various g^uiis. The continental nations of Europe have done but little in the manufacture of rifle-cannon throwing pro- jectiles weighing over 100 lbs. In France and Spain the cast-iron sea-coast cannon, corresponding to our 32-pounders, have been banded with steel hoops and rifled. In Russia 9-inch rifle-guns, made of Krupp steel, have been used to a certain extent, but it is imderstood that one or more of them have failed in service. In the matter of field artillery, most of these nations have rifled their bronze guns, thus making use of the material on hand. The Prussian field guns, however, are made of Krupp steel, and are breech-loaders. In Russia the Broadwell system of breech-loading has been introduced into the field service. A Table of JPbrei(/n Gannon, as given by Major Oicen, Ji. A. Nature of Gun. Weight Charce of Powder in terms of Projectile. Projectile. Frencli ^-pounder (bronze). Cwt 6i 13 56 534 63 1-10 1-10 1-9 to 1-13 1-10 1-10 1-9 Lbs. 25J French 30-pounder (cast-iron) 60 to 100 Prussian 12-pounder (Krupp steel) 13 Prussian — pounder (cast-iron) 57 Spanish 32-pounder (cast-iron) 61 AKMSTRONG PROJECTILES. 555 PROJECTILES. 14. Armstrong projectile. But one kind of pi-ojeotile is used in the Armstrong breech-loading guns for the iield service, and this is so constructed as to act as a shot, shell or case-shot, at pleasure. It consists— fig. 162— of a very thin cast-iron shell {A A), en- closing forty-two segment-shaped pieces of cast- iron {J3 B), built up so as to form a cylindrical cavity in the centre (Z>), which contains the burst- ing charge and the concussion fuze. The exte- rior of the shell is thinly coated with lead (C C), which is applied by placing the shell in a mould and pouring it in a melted state. The lead is also allowed to percolate among the segments, so as to fill up the interstices, the central cavity being kept open by the insertion of a steel core. In this state the projectile is so compact that it may be fired without injury ; while its resistance to a bursting charge is so small that less than one ounce of powder is required to burst it. When the projectile is to be fired as a shot, it requires no pi'eparation ; but the expediency of using it other- Fig. 163. wise than as a shell is doubted. To make it available as a shell, the bursting tube, the concussion and time fuzes, are all to be inserted; the bursting tube entering first find the time-fuze being screwed in at the apex. If the time- fuze be correctly adjusted, the slit?ll will burst when it reaches witliin a few yards of the object; or, failing in this, it will bui-st by the concussion-fuze when it strikes the object, or grazes the ground ntar it. If it be required to act as a canister-shot upon an enemy close to the gun, tlie regulation of the time-fuze must be turned to the zero of tlie scale, and then the shell will burst on leaving the gun. The explosion of one of these shells in a closed chamber, where the pieces could be collected, resulted in the following number of fi-a"-ments : — lOS pieces of cast-iron, 90 pieces of lead, and 12 pieces of fuze, etc. — making in all 217 pieces. The Armstrong projectiles for the muzzle-loading guns have 556 APPENDIX. ^ ( r u D ® K f 4 ®i ■ i® m 1® d /® ® ■■■■® (2) "^^ ^^ rows of brass or copper studs projecting from their sides to fit into tlie grooves of the gun, which are constructed on the shunt principle. Fig. 163 represents a 10-ineh Armstrong shell for penetrating armor plates. It is made of wrought-iron, or I low steel, with very thick sides. There is no fuze, the explosion resulting from the heat generated by the impact, and the crushing in of the thin cap which closes the mouth of the powder chamber. The sides and bottom of the shell being thick enough to resist crushing by the impact and also to resist the explosive force of the bursting charge, its efieot will, after penetration, be expended on the backing of the armor, or the decks which the armor Fig. 163. is intended to screen. Such projectiles ai"e called " blind shells." 15. Wliitwortli projectile.' The cross-section of the bore of the Whitworth gun is a hexagon with the corners slightly rounded. The projectile is first formed so that its cross-section is a cir- cle, and its sides taper towards both ends. The middle portion is then carefully planed off to fit the bore of the gun. Fig. 164 represents a Whit- worth blind shell for firing against armor plates. It is made of tempered steel, and each end is closed with a screw. To prevent the heat of im- pact from acting too soon on the bursting charge, it is surrounded by one or more thicknesses of flannel. Fig. 164. A t-inch shell of this kind has been found to have sufficient strength and stiffness to penetrate five inches of wrought-iron before bursting. 16. French projectile. The projectile used in the French Hold eervice is made of cast iron, and has twelve zinc studs on its nicies, arranged in pairs, so as to fit the six grooves of the gun. See fin;. 165. PROJECTILES. 557 For the larger cannon projectiles but three studs are used, and these are cast on the projectile, nearly opposite to its centre of gravity ; tlie bear- ing sides of the studs are faced with white met;il to diminish friction against the grooves of the bore. The shape of the grooves is such as to centre the projectile. The latter projectile is used with increasing, the former with grooves of uni- form twist. Russian, Austrian and Spanish artillery pro- jectiles belong to the studded, or button class, but differ from each other in the details of their con- Fig. 165. struotion. 17. Blakely projectile. Captain Blakely's projectile has an expanding copper cup attached to its base by means Hof a single tap-bolt in the centre (see fig. 166). It is prevented from turning by radial grooves cast on the surface of the bottom of the projectile, into which the cup is pressed by the charge. The angle between the curved sides of the cup and the bottom of the pro- jectile is filled with a lubricating material. On the forward part of the body are soft metal studs, more numerous than the grooves of the bore of the piece, that some of them may always form a bearing surface for the projectile against the lands. The driving sides Fig. 166. of the grooves are deeper than the other. 18. Scott projectile. The shell devised by Commander Scott, of the British Navy, for firing molten iron, is shown in fig. 167. It has three ribs cast upon it, which fit grooves so constructed as to centre it in the bore of the gnn when fired. The interior of this shell is lined with loam to prevent the heat of the charge from penetrating through to the bursting charge. It is supposed to be broken and its contents diffused on striking the object. .1 19. Parrott projectile. Capt. Parrott's projectile is composed of a cast-iron body and a brass ring cast into a rabbet formed around . Fiff. 167. 558 APPENDIX. its base (see fig. 168). The flame presses against the bottom of the ring and underneath it so as to expand it into the grooves of the gun. To prevent the ring from turning in the rabbet, the latter is recessed at several points of its circumference. Parrott's incendiary shell has two compartments formed by a partition at right angles to its length. The lower and larger space is filled with a burning composition ; the upper one is filled with a burst- ing charge of powder, which is fired by a time or concussion-fuse. The burning composition is intro- duced through a hole in the bottom of the shell, Fig. 168. which is stopped up with a screw plug. 20. Scheiible projectile. Schenkle's projectile is showfl in fig. 169. It is composed of a cast-iron body (a), the posterior portion of which is a cone. The expand- ing portion is a papier niache sabot or ring (b), which is expanded into the rifling of the bore by being forced on to the cone by the action of the charge. On issuing from the bore the wad is blown to pieces, leaving the projectile unencumbered in its flight. A great difficulty h.as been found in prac- tice in always getting a proper quality of material for the sabot, and in consequence, these projectiles Pig. 169. have not been found to be reliable. 21. Ilotchkiss projectile. The Hotchkiss projectile is com- posed of three parts: the body (a), — fig. 170— the expanding ring of lead (J), and the cast-iron cup (c). The action of the charge is to crowd the cup against the soft metal ring, thereby expanding it into the rifling of the gun. The time-fuse projec- tile has deep longitudinal grooves cut on its sides to allow the flame to pass over and ignite the fuse. The last rifle-projectile submitted by Mr. Hotch- kiss has an expanding cup of brass attached to its base in a peculiar manner. The cup is divided into four parts by thin projections on the base of tl e projectile.- This arrangement is intended to facili- tate the expansion of the cup and to allow the flame to pass over to ignite the fuse. Kg. 170. PROJECTILES. if) 9 22. Sawyer projectile. The Sawyer projectile has npon its sides six rectangiilaf flq,nges or ribs to fit into corresponding grooves of the bore. To soften tlie contact with the surface of tlie bore, tlie entire surface of the projectile is covered with a coating of lead and brass foil. The soft metal at the corner of the base is made tliickcr than at the sides to admit of being expanded into the grooves, and thereby closing tlie windage. In the latest pattern of Sawyer pro- jectiles the flanges are omitted, and the projectiles are made to tako the grooves by the expansion of the soft metal at the base; which is peculiarly shaped for this purpose. 23. Juincs projectile. The expanding part of James's pro- jectile consists of a hollow (c), — fig. ITl — formed in the base of the projectile, and eight radial openings (b), which extend from this hollow to the surface for the passage of the flame of the charge, which presses against and expands into the grooves of the bore, an envelope or patch (e), composed of paper, can- vas and lead, (a) represents the body of the pro- jectile, which in this case is a solid shot, {d) is a partition between two of the openings. In a later pattern of this projectile, the internal cavity and radial openings are omitted, and the outside is furrowed with longitudinal gi-ooves Fig. 171. which increase in depth towards the base of the projectile, forming inclined planes, up which the outer covering of lead and canvas is moved by the force of the charge and expand- ed into the rifling of the piece. 24. Dyer projectile. The Dyer projectile is composed of a cast-iron body (a), — see fig. 172 — and a soft m^etal expanding cup (J), attached to its base. The adhesion of the cup is effected by tinning the bottom of the projectile, and then casting the cup on to it. The cup is composed of an alloy of lead, tin and copper in ceitain propor- tions. This projectile, as improved by Mr. Tay- lor at the Washington Arsenal, gives good re- suits for even as large a calibre as 12 Indies. (c) represents a corrugated cap of tinnL'd sheet-iron, used with 3-in. projectiles to catcli Fig. 172. and direct that portion of the flame of the charge which escapes over the projectile on to the fuze to ignite it. 560 APPENEIX. Fig. 173. Fig. 174. 23. Confederate projectiles. The rifle-projectiles used by the Confederates in the late war, belonged, with a few exceptions, to the expanding class. Fig. 173 represents a Confederate wrought- iron solid shot, for use against iron-elads. For the larger sizes this shot is formed by welding rings around a bar of iron and then turn- ing the mass to tlie proper size. It has an annular-sliaped cup at the base for the purpose of expansion. Fig. 174 represents a shell with a copper ring (b) fitting into a rabbet formed around its base in casting. This projectile would seem to resemble the Parrott projectile in its construction. The lower edge of the band, however, projects below the bottom of the base, which in Parrott's it does not. Recesses are formed in the sides of the rabbet to prevent the ring from turning. The projectile represented in fig. 17.') has a thick circular plate of copper attaclied to its base by means of a screw-bolt at its centre. To prevent it from turning around this bolt there are three pins, or dowels, fastened into the base of the projectile, and projecting into correspond- ing holes in the circular plate. This plate is slightly cupped, and the angle between it and the bottom of the projectile is filled with a greased cord for lubricating the bore of the gun. Fig. 175. ■EXPERIMENTS ON AKxMOK PLATES. 5(51 Fig. 176. Fig. 177. Fig. 176 represents a projectile of the Blakely class, with its ex- panding cup of copper (a). Instead of the soft metal studs ivhich are placed on the forward part of the Blakely projectile, this projectile has a raised band carefully turned to fit the bore. Fig. 177 represents a Reod projectile, in which the expanding cup is made of copper, as shown at (a). This cup is placed in mould, and the body of tiie projectile is cast upon it. EXPERIMENTS ON ARMOR PLATES. 26. Captain Woblc's conclusions. The following conclusions are drawn by Captain Noble, R. A., fi'om the results obtained in England fiom various experiments carried out under the direction of the Ordnance Select Committee : 1. Where it is required to perforate the plate, the projectile should be of a hard material, such as steel or chilled iron. 2. The form of head best suited for the perforation of iron plates, whether direct or oblique, is the pointed ogeeval. 3. The best'form of steel shell at present known is that in which the powder can act in a forward direction, and which is furnished with a solid steel head in the form of a pointed ogeeval. 4. When chilled iron can be made of the best quality, it i? al- most, if not quite, as good as ordinary steel for solid shot ; and when the projectile can perforate with ease, the chilled shot is mora formidable than steel, as it enters the ship broken up, and would act as grape.* * The introduction of chilled iron is due to Major PaUiser, who has devoted much time and attention to the subject. 562 APPENDIX. Wo liavc every reason to hope that chilled sliells can be cor.- Gtructcd, which will prove equal, if not superior, to steel.* 5. To attack well-built iron-clads effectively, the guns should be, if possible, not under twelve tons weight and nine inches calibre, firing an elongated projectile of two hundred and fifty pounds, with forty pounds of powder. 0. When the projectiles are of a hard material, such as steel, the perforation f is directly proportional to the " work" in the shot, and inversely proportional to the diameter of the projectile ; and it is immaterial whether this '' work" is made up of velocity or weight, within the usual limits which occur in practice. 1. The resistance of wrought-iron plates to perforation by steel projectiles varies as the squares of their thickness. 8. Hitting a plate at an angle diminishes the effect as regards the power of perforation in the proportion of the sine of the angle of incidence to unity. 9. The resistance of wrought-iron plates to perforation by steel shot is practically not much, if at all, increased, by backing simply of wood, within the usual limits of thickness ; it is, however, much increased by a rigid backing either of iron combined with wood, or of granite, iron, brick, etc.J 10. Iron-built ships in which the backing is composed of compact oak, or teak, offer much more resistance than similarly clad wooden ships. 11. The best form of backing seems to be that in which wood is combined with hoi-izontal plates of iron, as in the " Chalmer," " Bellerophon," and " Hercules" targets. 12. An inner iron skin is of the greatest possible advantage ; it not only has the effect of rendering the backing more compact, but it prevents the passage of many splinters, which would otherwise find their way into the ship. No iron-clad, whether iron-built or wooden converted, should be without an inner iron skin. *It is not meant by this that cMlled iron would prove superior to the very best tool steel ; but that it will be as effective as the ordinary steel hitherto used in the manufacture of projectiles. f Or power of complete penetration. X That is to say, as a sliot which is capable of breaking a hole through a 4i-inch plate unbaclved, wiU be also capable of doing so if the plate be only backed by v;ood, to the extent that, were the plate taken off the backing, the piece of iron where the shot had struck would fall out. EXPERIMENTS ON AEMOE PLATES. 563 13. The bolts known as "Palliser's bolts" are, so far as known at present, the best for securing armor plates. In these bolts the diameter of the shank is reduced to that which it is at the screwed end. 14. Laminated armor is much inferior to solid armor. Captain Noble then proceeds to make the following remarks on the relative merits of rifled and smooth-bored guns against armored vessels, viz. : There are two metbods by which an iron-clad vessel can be de- stroyed by the fire of artillery : 1. Hadking (American system), or the impact of heavy shot of large size moving at low velocities, and intended to shatter the ves- sel's armor, and by repeated shakes ultimately to knock the whole structure to pieces. 2. Punching (English system), oi- the penetration of the vessel's side, either by elongated shot or shell, intended to kill the crew, blow up the magazine, damage the machinery, and sink the vessel by holes made through her at or near the water-line. Both these systems have their advocates, and there is undoubtedly a great deal to say on both sides. All warlike operations tend to the crippling of your enemy ; and that system is evidently the best which will cripple him in the short- est time, in the easiest manner, and at the least possible expense. • Now, time is an element which will largely enter jnto considera- tion in future actions with iron-clad vessels. Suppose two opposing • iron-clads to meet — one armed with guns on the " racking" system, the other with guns on the " punch- ing" system, it is probable that the vessel which could send her shot clean through the side of her adversary would have the greatest ehance of reaching a vital part in a given time. Besides which, a " punching" shot is usually an elongated rifle projectile animated by a moderately high velocity, and has consequently & flatter trajectory than the " racking" shot, which travels at a low velocity ; and as ac-i curacy and a flat trajectory are closely allied, the " punching" sys- tem would gain another chance, viz. : that of making the greatest number of hits for a given number of shots. Suppose an iron-clad is desirous of running past a fort which de- fends an important harbor or roadstead. She would, if possible, probably pass at a rate of ten miles an hour. The fort in this case would only have time to fire a few rounds at her, and if the eflfect of l)Qi APPEKDIX. those rounds was merely an external " racking," the vessel might re- ceive no real injury at all — nothing, at least, which would in all likelihood stop her. On the contrary, a happily directed " punching" shot would have the chance of destroying the machinery, blowing up the magazine, or establishing a leak at the water-line. In attacking an iron-clad by the " racking" system, the whole ef- fect is directed against the casing or armor-plating of the vessel, which, for all offensive purposes, is harmless; the enemy which we want to cripple are the men and guns behind the armor. It appears from these considerations that an attack on the " punching " system will probably be attended by gain in time, as the vital parts of the vessel cannot be reached so quickly by an at- tack on the "racking" system. Even were an enemy's ship ulti- mately shattered and her offensive power destroyed by the effect of heavy blows, this result might not be effected hefore she had ac- complished her object, if not altogether. The attack on the " punching" system is carried on in an easier manner than that on the " racking" system. The former employs light rifle guns, from six to twelve tons; the latter, unwieldy heavy ordnance of from twelve to fifty tons. The " racking" projectiles are heavy cast-iron shot, fired with relatively small charges, and the loading and working of such projectiles and guns cannot be carried out as easily or expeditiously as in the case of a system which uses a lighter shot and relatively ^arger charge.* The question of expense is one which, although it should come last in an inquiry of this nature, is too often made the most import- ant consideration. If, however, we compare the cost of the 9-inch rifled twelve-ton gun as fairly repi-esenting the punching system, and the American 15-inch twenty-ton smooth-bore gun as representing the racking system, we shall find -that the total cost of gun, carriage and one hundred roinids of ammunition is very much the same for each. On the one hand, the money will have procured a gun wliich can *The present English system comprises a rifled gun tlirowing an elongated eliot "witla a moderately liigb charge, with a view to penetration. If, however, it be desirable to adopt the opposite system, either altogether or in part, there will be no difficidty in employing lieavy shot and low charges with our rillo- guns. The Americans, however, cannot apply our system to their smooth-boro guns, which is a point in our favor. _ EXPERIMENTS ON AEMOE PLATES. 565 send a shot, and possibly a sliell, through the strongest iron-clad yet afloat at one thousand yards' range. On the other hand, a gun will be obtained which cannot pierce the above ship at any distance whatever ; whose shot, at one thou- sand yards, would, if cast-iron, merely indent the armor and fall back broken into the water, and if steel, would merely lodge in the ship's side, and whose shell would be absolutely worthless against an iron-clad, and even against wooden ships or earth-works, inferior to the 9-inch rifle shell, both in accuracy and bursting power. Remarks by the Author. — It is probable that Captain Noble bases his estimate of the power of the American 15-inch smooth- bored gun on the impression that it can only be fired with low charges of powder. It has been shown, however, that an initial velocity of 1200 feet can be easily obtained with this gun. A pro-, jectile, therefore, which weighs 450 lbs., fired from it, will have a striking velocity at 1000 yds. of 961 ft. equal to a total force of 3230 foot-tons, or 69.3 foot-tons per inch of the shot's circumference — a force, as shown by Captain Noble, more than sufBcient to penetrate the Warrior target. . It was with a force probably less than this, that the side of the iron-clad Atlanta was smashed in, and the ram Tennessee ' was disabled, each by a cored 15-inch shot made of ordinary cast-iron. The power of the lo-inch gun, however, is not limited to 1200 feet initial velocity. Several of these guns of the army pattern have lately been fired with charges as high as 100 lbs. of mammoth powder, giving an initial velocity of 1500 feet. In one case, as many as 100 rounds have been fired with this charge with no mate- rial enlargement of the bore. Within the limit of effective iron-clad warfare, the 15-inch gun- has great accuracy of fire. In the trials lately made at Fort Mon- roe, it was shown that the accuracy of this gun at 1500 yds., with a charge of 100 lbs. of powder, was fully equal to that of the best rifle practice, and that while the least elevation of the rifle-guns was, for this distance, 3° 10', that of the 15-inch gun was only 2° 25'. The' latter, therefore, has a 'flatter trajectory within this distance, and the projectile being round, has greater accuracy in ricochet fire. The advantage, however, which rifle-guns have of projecting . loaded shells of peculiar construction (see Armstrong and Whit- worth projectiles), so as to penetrate and explode in the sides of iron-clad vessels, is certainly an important one, and may, perhaps, outweigh, in actual service, the smashing power claimed by the ad- {)«« APPENDIX. 521 cs o e c i il Eh o S -^ .a o (^ n e3 1 s dTi) . 1 gj 0) ¥ 09 ce 1 ■§4 -a »<.ao I. 'a a en ta S a .S a § 2-1 i 4^* in 07 "H-o s ■? 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The second shot passed clean through, carrying with it the piece of plate and many splinters. i plate to a depth of 5 in. id. A steel shot (roinui) and remained in b;icl;- Iged and cracked. Eiinjfo ,o g 1 1 or is o-o « o « lIlN S = 2 . 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S3 <0 » U CD . 0) -p. 4-) jJ ^ a3 f O ■^02 B r^ bD ' ^ en *J3pAV0J JO puujg; M 4 ,• c 2 i'S . t- s-:^S aS§ .S bc-Z r'fi^ ^N ^^"^ S.3 = i CM c 03 a •-•T fell ^3- ■^ •;3 g=.-B £ "Lor den,' plate j£ en Canals, and on the Flow through Submerged Orifices and Diverging 'I'uli s. Vfith2o copperplates, beautifully engraved, and about 100 new pages of text. KiI■lc^vood on Filtration. 4tc>. Clotli. .SlS.OO. IIepoiit ox the Filtjjatiox of River Watkk.s, for the Supply of Cities, as practised in Europe, made to the Board of Water Commis- .sioners of the City of St. Louis. By James P. Kirkwood. Illustra- ted by 30 double-plate engravings. SCIENTIFIC BOOKS PUBLISHED PA' liogers' Geologj'' of Pennsylvania. ?, Vols. 4to, with Portfolio of Maps. Cloth. .fSO.OO. I'liK Geology oi' Pennsylvania. A Goveinnient Survey. AVitli a gen- eral view of tlie Geology of the United .States, E.ssays on the Coal For- mation and its Fossils, and a desciiption of the Coal Fields of North America and Great Britain. 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