artillery

Field cannon 18th century

Coehorn mortar 18th century

The cannon was the first internal combustion engine, made possible by the discovery of nitrates

The smoothbore cannon, first appearing in the early 14th century in Europe, assumed its classic form at the beginning of the 17th century, which persisted unchanged to the mid-19th century, when it was superseded by the breechloading rifled gun. It perhaps still remains in modified form as the infantry or trench mortar, and a few other smooth-bore weapons. It was simply a strong cylinder permanently closed at one end, and temporarily closed by a cannonball towards the other end, between which a charge of explosive was placed. When the charge was ignited through the touch-hole, it exploded, or changed to highly compressed gas, very quickly, expelling the ball to do whatever service was required of it. This service was smashing a wall, or dismembering men and horses, or crashing through the wooden side of a ship, all frequently required duties. The cannon was an early internal combustion engine, as the fusion bomb is today, with few constructive uses. This paper is devoted to the origins of gunpowder and cannon, and to firearms lore. Developments since about 1860 are not included, except incidentally. Unfortunately, I am not able to provide graphic illustrations here, but many are available in the references.

The invention of the cannon is a very imperfectly known story, although the main themes and approximate dates are clear. The dates, places and protagonists of the inventions of gunpowder and the cannon cannot be determined, because the invention was not a simple act. Gunpowder had to be invented first, but even here gunpowder is not one substance, but many, of differing properties. Gunpowder depends on the availability of pure nitrates or saltpetre, which does not occur naturally, and will not be found by accident. Therefore, the origin of cannon begins with a question of chemical engineering. The best chemical theories of the time, around AD 1000, were in all respects those of antiquity and utterly futile in the solution of this problem. Nevertheless, gunpowder was developed, through blind trial and error. This is a story that clearly illustrates the power of modern chemistry, which scarcely existed before 1800.

One must clearly define an invention before the details of its invention can be determined. For example, a modern Renaissance scholar, Charles Nicholl, recently notes that the excellent Leonardo 'anticipated Newton by two centuries' in placing a glass of water in a sunbeam and noting the pretty colours. These colours were well-known in antiquity. What Newton did was explain them, but the modern literary scholar has no more concept of what such an explanation could possibly be, and that there is more to the world than surface qualities, than a Scholastic (which Leonardo was not). Newton, indeed, purchased his prism at an optician's, where they were presented for sale precisely for the production of these colours. Dr Nicholl is not the only one to make such assertions; they are very common.

The fundamental inventions of gunpowder and cannon had been made by 1300, but the sources are rare, difficult to interpret, hard to date, and often contradictory. The best guess is that gunpowder followed quickly after saltpetre was discovered by Chinese alchemists around AD 900, and that cannon were invented in southern Europe just before AD1300. The period 1300-1600 saw the cannon perfected, chiefly in Europe, and it assumed its classical form. Small arms appeared in this period, revolutionizing armies and warfare. Technical terms are often obscure, however, and writers can be biased and their histories fanciful. The history of developments after 1600 is much clearer and better documented, with reliable drawings and accurate dates. One must always beware of taking some later creation as original evidence, especially pictorial evidence. For example, there are excellent drawings of the siege of Stirling Castle by Edward I in 1304, that look like witnesses of how things appeared, but they certainly are not. There is not a scrap of graphic evidence of how the siege actually appeared, only a few scraps of parchment with writing, and the scene is an artist's reconstruction. Many sources contain drawings added to the manuscript at a much later date, which are in the same vein.

The name cannon comes from the essential part, the cylindrical bore or barrel, probably through the Latin canna, for a reed, with the Italian augmentative suffix -one, making cannone, and joining the vernacular in the 14th century. Indeed, the earliest Chinese and Arabic firearms used bamboo tubes, cannae, as barrels, and shot arrows. The word canon was used in Latin for a gun (1326 in Italy, 1418 in England), but this is just a Latinized cannone, assimilated to an existing word. Curiously, the word for the military authorities supplying cannons and gunpowder, ordnance, comes from ordinance, which is the real meaning of canon. canale is recorded in 1461 for a gun, referring to the barrel. Bombardum was used for cannon and cannonball as early as 1430, and bombator is known from 1456 for a gunner, or or bombardiator from 1547. These come from the earlier word for a heavy siege catapult. Gunna and gonna are known from as early as 1370 for a gunner or gun, especially in England, but the derivation from Gunnhilde, mangonel or engine is not convincing. Gun has now superseded cannon in common use. Pulvis for gunpowder is recorded from around 1400, and in particular pulvis facticius from 1575. Pulvis pyxidis ('small-box powder') is also seen. The words used in German (büchse - box) and other languages are similarly varied. A good deal of confusion exists in the historical use of terms relating to cannon, especially between traditional siege weapons such as catapults, scorpions, mangonels and trebuchets, and gunpowder cannon. The story of cannon begins with gunpowder.

Gunpowder

The propellent gunpowder was the essential requisite for using a cannon, and it is not something that is easily made, nor found by accident. On Star Trek, Captain Kirk mixed diamonds, sulphur and saltpetre and shot an alien with an improvised gun. It is not that simple, by a long ways, as in that childish imagination. The first step is to obtain pure potassium nitrate, called sal Petrae, Peter's salt, saltpetre. Nitrates were not recognised in antiquity, where words like nitron always referred to carbonates or bicarbonates, and never occur in pure form in nature. Chinese alchemists seem to have discovered nitrates during the Sung dynasty, perhaps around AD 900, as a white, crystalline powder that cooled water when dissolved in it, and deflagrated vigorously when thrown on a fire. It was this last property that was new and exciting. Nitrates came to Europe as Chinese snow through trade routes in the following centuries as an alchemical curiosity.

Incendiary and poisonous preparations had long been exploited in siege warfare. These depended on natural petroleum, sulphur, and other combustibles, and were delivered from catapults or as smokes or jets. Greek Fire, which is first noted in the seventh century AD, was especially effective. It was a Byzantine military secret, and called Sea Fire by them because of its great effectiveness in naval combat. They did not call it Greek fire, because they did not call themselves Greeks, but Romans. A preparation of this name became widely used in mediaeval siege warfare which was really just the customary incendiaries with the addition of saltpetre. This made the fire independent of atmospheric oxygen, and caused it to burn intensely. The composition of the original Sea Fire was lost. Some now think it contained saltpetre, but Partington thought the secret ingredient was distilled petroleum, and I tend to agree with him, since I cannot accept the availability of purified nitrates in the seventh century, and his is a very well-informed guess.

Saltpetre was one of the costliest expendables ever required in warfare, so there was ample incentive to use the least amount possible. Mixtures in which pure nitrates are not predominant deflagrate only, and do not explode. The Chinese, and others, surely possessed such mixtures as soon as saltpetre became available. The fire lance was probably the next step. This was a bamboo tube several feet long, drilled through the joints and wrapped with strong twine to keep it from bursting, and attached to a long heft with which to hold and aim it. It was loaded with a deflagrating powder and various projectiles, in fact much like a kind of Roman candle. It was lighted from a fuze projecting from the muzzle, whereupon it would discharge its fire, gases, and projectiles to the front. Turned around so it discharged to the rear, it made a rocket, stabilised by a stick behind it, and perhaps with an iron point on the front. Weapons of this type were used in China by the 13th century, and spread through the Mongols and Tatars to the Arabs and to India, around 1250. One example shows a tray held like a rifle, in which several cartridges, small fire lances, could be exploded one by one.

The more saltpetre that the mixture contains, the quicker and more fiercely it burns. The Chinese had firecrackers for a very long time, but they contained no gunpowder. They were simply pieces of bamboo that would crack loudly when thrown into a fire, and thereby scare away evil spirits. The proto-gunpowder, when confined in a strong paper tube the size of a finger joint, would make a terrifying lound bang, and these new firecrackers were very effective against evil spirits. Roger Bacon already knew about this in 1216, and described it in Epistolae de Secretis Operibus as a device to make noise like thunder and a flash like lightning, giving an anagrammatic recipe for the powder. The invention proceeded no further in China, beyond incendiaries, fire lances, and firecrackers. European gunpowder and cannon were reintroduced to China under the Ming dynasty by the Portuguese and others.

The place and time of the invention of the cannon is unknown, but its evolution from the fire lance among the Turks, Arabs and Europeans can hardly be doubted. In 1304, Edward I made no use of cannon at Stirling, although he ordered saltpetre for Greek Fire, but by 1341 the castle was defended by the Scots with guns. Guns are reported at Crécy in 1346, but in a minor role. The Venetians are said to have used cannon for a siege in 1380, as did Alfonso XI about the same time against the Moors in Spain. Poudre à canon is recorded in 1338. The Osmanli Turks used large cannon at the final siege of Constantinople in 1453, by which date the innovation was widely known in the West. The bombard of 3 ft calibre throwing a 600lb stone at Constantinople seems very large for the time, but apparently such large guns actually existed.

In Europe, a monk of Freiburg, Constantine Anelzin, was credited with the discovery, but he is none other than Brother Berthold Schwartz, the legendary and imaginary German inventor of guns and gunpowder. An excellent and documented analysis of these matters can be found in J. R. Partington, A History of Greek Fire and Gunpowder (Baltimore: Johns Hopkins, 1999), first published in 1960. Chinese sources like to represent later, or foreign, inventions as earlier native ones for the greater glory of China, and much care is advised in accepting these claims. Incidentally, the first Roman embassy to China reached there by ship in AD 166, and the silk trade flourished for centuries, so the transmission of western influences can hardly be doubted. A Roman legion captured by the Parthians was sold to a Chinese emperor, and many of the men remained even after they were ransomed, so valued had they become as engineers. Some writers have even suggested that gunpowder reached China from the West. The legend of Black Bert was advanced by German students of military science in the 19th century to trace gunpowder and cannon back to German orgins. Developments seem concurrent across Europe in the 14th and 15th centuries. We shall return to the lore of cannon later, after the following chemical episode.

The constituents of gunpowder, the modern black powder, are potassium nitrate (saltpetre), sulphur, and carbon in the form of wood charcoal, in the approximate ratio by weight of 4:1:1 for a strong cannon powder to 10:1:2 for a pistol powder. A modern average ratio is 75:11:14. This is no secret, and will not aid evil teenagers to build bombs, since there are much better modern alternatives, and you will see that today's teenagers are not likely to have the patience to get the process correct. The saltpetre is purified, mainly of common salt, lime and dirt, by recrystallization, the sulphur by distillation, while the charcoal must come from the best, uniform wood for the best powder. These ingredients are coarsely ground, and put in an iron pot, then moistened with water, alcohol, vinegar, or urine. Which liquid matters very little, since the objective is to extinguish any sparks. The Encyclopedia Britannica article on gunpowder leaves out this essential fact. The mixture is then constantly bruised by an iron rod lifted and let fall repeatedly, in a stamp mill, for twenty-four hours. One water-driven powder mill can make as much powder as a hundred men with mortars and pestles. Unless the ingredients are tediously mixed this way, they will only burn or fizzle when ignited, not detonate. Early powder was ground on stone tablets, not mortars, while later mills used rotating wheels.

The saltpetre can be any nitrate salt, but KNO3 is the best because it is least hygroscopic. Ca(NO3)2 and NaNO3 absorb water and cause the gunpowder to spoil more rapidly. Gunpowder spoils by absorbing water, and calcium nitrate gunpowder must be used almost immediately. In fact, the principal role of the sulphur appears to be to improve the shelf life of the powder. The production and purification of saltpetre is the key to understanding the history of gunpowder. Nitrates appear in low concentrations in stable floors, walls, cave deposits and other places where it has been produced from animal wastes or bacterial action. The nitrous earth is leached, treated with wood ashes to precipitate the calcium and magnesium and replace them by potassium, and the saltpetre separated from sodium by recrystallization from cool solutions, in which common salt remains soluble. Until rich mineral sources of nitrates were discovered (Chile saltpetre, sodium nitrate), they had to be extracted laboriously in this way. Gunpowder was as valuable as the cannon themselves, and its supply became a national concern, with the King owning stable floors and such. In the 18th century, India became a large exporter of nitrates, a trade controlled by the English and the Dutch. Nitrates are now obtained by oxidizing ammonia, which is synthesized directly from atmospheric nitrogen by the Haber process. A chemical equation for the reaction occurring when gunpowder explodes is 2KNO3 + S + 3C = K2S + N2 + 3CO2, but in actuality the reaction is much more complicated.

The saltpetre and sulphur must be finely distributed in the micropores of the charcoal, so the kind of wood used for charcoal has an important effect. Willow is reputed to be the best, and was used by the Chinese. Charcoal is a special kind of graphite with many loose bonds and active sites. Ordinary graphite would not work. Early gunpowders had strange and useless additions for alchemical reasons, or to make the smoke poisonous. Certain ingredients were reputed to make the smoke move against the wind. Using a more vigorous oxidising agent, such as potassium chlorate, KClO3, makes the powder impossibly sensitive and dangerous, as Berthollet discovered in 1786.

This is not yet all there is to gunpowder. The flour or meal is then moistened appropriately to make a paste, and pushed through a sieve to reduce it to small grains, of which the size and shape are very important. This is called corning the powder. Swiss powder was reputed the best in Europe in the 18th century, and it had round, uniform grains. The dried grains were then packed in barrels, and carefully kept dry. Gunpowder had become an important commodity by the 18th century, and was widely traded. Fireworks (French: artifices) were by then already elaborate and popular. Fireworks later gave rise to the rocket, which projected a ball or bomb without the use of a cannon. War rockets had been used in China since about AD 1200, fire lances turned around and called flying rats. Congreve's famous rockets were first used against Boulogne in 1805. Rockets went out of favour around 1850 as more accurate and powerful guns were developed.

Fine powder, meal or flour gunpowder, merely burns rapidly without detonating, so it was suitable for early, weak cannon. The snap of a firecracker is due to the fracturing of the enclosing paper, not the detonation of the powder. Grains, however, will detonate by means of a shock wave and release the gases much more rapidly, making a stronger gunpowder suitable for later cannon. Early powder was also closer to a 1:1:1 ratio, which also made it burn more slowly.

We understand, therefore, that anyone trying to make gunpowder without knowing the tricks will either blow him- or herself up, or only achieve an incendiary powder, not the useful low-explosive or propellent. One of the du Ponts (American gunpowder manufacturers who fled France after Napoleon's defeat, adding the 'du' ennobling themselves later in America) blew up himself and a gunpowder mill in Wilmington, Delaware in the early 1800's. There is a good reason why gunpowder factories were made of isolated buildings surrounded by earthen ramparts.

The French authorities made extensive gunpowder tests in the arsenal at Essonne on 12 February 1756 to determine the best formula. To test the samples, they used an éprouvette, a small mortar of 7 inches calibre (diameter of bore) that projected a 60 lb copper sphere using a standard charge of 3 ounces of powder. To be acceptable, a powder had to give a range of about 300 feet (50 toise). The normal European powder, consisting of 2 ounces, 5-1/3 grains each of sulphur and charcoal to 1 pound of saltpetre, achieved a range of 448 feet. This corresponds to a muzzle velocity of 120 ft/sec, or about 82 mph, which is quite low, corresponding to the small, economical charge of powder.

When gunpowder explodes, it increases in volume about 4000 times at normal pressure, so the effect is to produce a highly compressed gas behind the cannonball in a very short time. The products are 40% gaseous, and 60% solid. The solid fraction is expelled as a dense white smoke, which gives away the position of a battery as soon as it is fired. The combustion of gunpowder does not depend on atmospheric oxygen, because the oxidiser, saltpetre, is part of it.

After the 1860's, black powder was replaced by nitrocellulose, or guncotton, made by treating plant fibre with concentrated nitric and sulphuric acids. This substance, discovered by Schönbein in 1845, naturally burns slowly, making it a good propellant, and its products are completely gaseous, so little smoke is produced, which gave it its name of smokeless powder. Unlike black powder, it is rather unstable, and the early product, which contained residual acids, could explode spontaneously. Early guncotton works exploded in both England and France. Gelatinising the product with acetone, and the use of stabilisers discovered in the 1880's rendered it safe, however. Vieille's Poudre B of 1886 was used in the new French leBel rifle. The product is rolled into thin sheets that are then cut up as required into grains. Some smokeless powders ('double-base') also contain nitroglycerin. Nitroglycerin is a high explosive, discovered by Sobrero in 1846, and cannot be used as a propellant. Alfred Nobel found out how to make it safe to use in 1867 as dynamite, as well as a solvent for guncotton. Ballistite, Nobel's double-base propellent, had about equal amounts of nitrocellulose and nitroglycerine. Black powder remained the best explosive for coal-mining, since it sprung the coal down without shattering it. There was a long, and largely futile, search for safer blasting compounds, called permitted explosives, for coal mining that would not ignite methane.

After 1800, the New Chemistry discovered many new explosive compounds. Guncotton, already mentioned, was one of these that could serve as a propellent. Nitroglycerine, and other high explosives, are good for demolition and shattering, but cannot be used in cannon. Perchlorates, such as KClO4 are more vigorous oxidizing agents than nitrates, but always explode during manufacture if you try to substitute them for nitrates. Silver azide, AgN3 is very explosive, releasing nitrogen. Mercuric fulminate, Hg(CNO)2, is also explosive. All these compounds--perchlorates, azides, and fulminates--are, unlike gunpowder, sensitive to shock. They are now used in small portions to initiate the explosion in other explosives which are relatively insensitive to shock, and therefore safe to handle. The initiators are kept separate from the main explosive until the moment of use.

Cannon

We have mentioned that the bamboo fire lance was the ancestor of cannon. In Europe, this technology met that of the iron forge and the bell foundry, so that metal cannon soon replaced those of bamboo, leather, wood or stone--any cavity can serve as an impromptu cannon. The first metal cannon were made from iron bars welded together side by side in the form of a cylinder strengthened by iron hoops, (suggesting the term barrel), and the first cannonballs were often of stone. Some cannon were made in two parts, barrel and chamber, separately loaded and wedged or screwed together for firing. Sometimes the breech of the gun was an open box, and the chamber wedged into it. Great numbers of unrecorded or famous gunners (such as Charles the Bold) met their ends from burst guns, or in making gunpowder, until relatively safe procedures were developed. This may be a good reason why the Chinese were satisfied with only noise and flame. In some historical accounts, early cannon called bombards were confused with catapults of that name, also used as siege engines, so that some impossibly large early cannon are recorded. From the cannon of various sizes, the field cannon on wheels, the musket, and the pistol were developed, each with its own style of mobility and scope of use.

The best cannon were cast in bronze, and were bored so that the stone or lead cannonballs fit closely, without packing. Gun metal was 9 parts copper to one part tin, a different alloy than that used for bells. The guns were provided with trunnions so that they could be accurately elevated when mounted in sturdy wooden carriages, or at least with rings for attaching ropes for lifting or restraint. These cast guns had a much better range than the earlier crude cannon, but were normally used at only slight elevation--point blank, it was called. Cast iron was a much cheaper material than bronze, and when it became available, it was used not only for cannonballs, where it completely superseded stone by the end of the 16th century, but also for the cannon themselves. This was a very early use of cast iron. If the casting was not very skilfully done, and the iron free of phosphorus, cast-iron cannon tended to burst rather easily. The French did not trust them, but the English made good ones.

After casting, the cannon was bored to make the barrel accurately cylindrical. The cannon was held either vertically or horizontally and rotated about its long axis, while the boring tool was fed into one end by gearing. After this, the touch hole was drilled out with a drilling machine, perhaps one using a bowstring to rotate the drill.

The classic cannon had a characteristic shape, tapered from base to mouth. There were rings around the barrel as a decorative feature that recalled the hooped barrels of much earlier times. From the base of the cannon towards the muzzle, these were called the base, ram force, trunnion, cornish, and mouth rings. The base of the cannon was provided with a small ball called the cascabel (a Spanish word) for help in pointing the cannon. This term later referred to everything back of the base ring. Originally, this might have been a rather long rod instead of a ball. The charge extended from the base ring to the ram force ring, the distance giving guidance to the gunner in charging his piece. The trunnions are the cylindrical extensions used to mount the gun in its carriage, and to permit it to be elevated and depressed. The elevation could be set and held with wedges between the cannon and its carriage, or by a screw. There were often rings and ears for managing the cannon with ropes.

To fire a cannon, this was the drill. A swab was doused in a bucket of water and used to thoroughly moisten the bore of the cannon, extinguishing any embers that might remain from a recent firing. The correct amount of gunpowder was poured into a sort of shovel from a cask, and emptied at the base of the bore. It was then rammed firmly back behind a wad or plug of wood or cloth or some such substance (sometimes a space was left between charge and wad). This wad served as a gasket to contain the gases when the charge was detonated, and as a piston to push the ball out of the muzzle. The ball was then put in the bore, and rammed firmly against the wad. Meanwhile, the gunner poured gunpowder in the touch hole. When the command to fire was given, he took a slow match that was kept burning, or a red-hot rod, and brought it to the touch hole, igniting the gunpowder trail, which then burnt quickly down to the charge and ignited it. The burning match was held in a portfire. When the chamber pressure rose to the critical level, the charge then detonated, and the cannon discharged the ball at practically the speed of sound.

In the 17th century, it was taught that the ball left the cannon travelling in a straight line, in what was called violent motion (due to the explosion). At the end of its trajectory, it struck the ground falling vertically, in what was called natural motion (due to gravity). Connecting these two regimes was a circular segment of what was called mixed motion. This was complete rhubarb, but as it was difficult to see the actual path of a cannonball, this scientific description was plausible. Tartaglia, however, asserted that the maximum range was achieved at an elevation of 45*, and that no part of the trajectory was straight. Galileo showed that the trajectory in the absence of air resistance was a parabola in 1638. The Englishman Anderson pointed out some effects of air resistance in 1674, and also accepted the parabolic trajectory, but maintained that there was still a straight segment near the cannon. After Newton finally explained mathematically how to analyze the motion rationally with allowance for air resistance proportional to the velocity, Benjamin Robins finally took air resistance properly into account, finding it increased rather as the square of the velocity, and actually measuring air resistance and muzzle velocities accurately. For any practical prediction of trajectories, air resistance must be taken into account.

Gunners used several kinds of mathematical instruments in their trade. Internal and external calipers were necessary to determine the size of the bore and the diameter of the cannonballs. Cannonballs were classified by weight. By the last part of the 17th century, a cannon was described by the weight of ball it fired, as a 'six-pounder,' for example. However, this designation depended on the material assumed for the cannonball. In Germany, stone balls were assumed, for example, but iron was the eventual standard. The use of the diameter of the bore instead, the calibre, was much later. The weight of a cast-iron cannonball in pounds is 0.136 times the cube of its diameter in inches. The gunner's quadrant (invented by Tartaglia) was put in the mouth of the cannon to determine the elevation of the barrel by means of a plumb bob. A good display of these instruments can be seen in the Science Museum in London.

English cannon, like others, were given names that indicated their sizes. Falcon, saker, demi-culverin, culverin, demi-cannon, cannon and basilisc described calibres from 2-1/2" up to 8-3/4", and weights from 800 lb up to 9000 lb. The middle-of-the-range culverin was 5-1/2" calibre (about a 20pdr), with a range of 460 yards point-blank, and 2650 yards when elevated by 10*. This implies a muzzle velocity of at least 865 fps, or 590 mph.

An Ordinance of 1732 standardised French cannon as 24-, 16-, 12-, 8-, and 4-pounders. The 24-pdr had a 5-2/3 in bore, a barrel 9 ft 6 in long, and weighed 5400 pounds. Its overall length was slightly more than 11 ft. The length of the barrel was 20 times its diameter, or 20 calibres, which was typical. Larger cannon were rejected as too dangerous and unreliable. Later in the century, the Carron Iron Works on the Firth of Forth, then having more blast furnaces (4) than any other iron works in Great Britain, began supplying shorter cannon that fired the same weight of shot as the long cannon. These were called carronades, and were popular with the British Admiralty, since they enabled a ship to have a heavier broadside because they were lighter and could be used on upper decks. Their range was not as great as that of the long guns, however, so they often put the ships carrying them at a disadvantage. The Admiralty preferred the economy (it did not even encourage firing practice).

French cast-iron cannon had a touch hole that was drilled in a copper plug which was hammered into the base of the cannon. The reason for this was probably to prevent stress concentrations that tended to burst cannon in this point when a small touch hole was used, but this is only a guess. The end of the bore was usually rounded out to a spherical shape to hold the charge.

A peculiar type of cannon was the short-barreled mortar, named from its resemblance to a mortar for grinding. Early bombards were usually mortars. The first mortars appeared around 1420. The barrel was much shorter in terms of its diameter than that of the usual cannon, perhaps 8 calibres. The short barrel might occupy only about half the length of the piece, the other half a chamber of smaller diameter to hold the charge of powder. It fired heavy balls or shells at elevations greater than 45* for use in siege warfare. The balls would, for example, sail over walls to come down inside a fort and roll around, as recommended by de Vauban. Huge mortars often feature in photographs of the American Civil War of the 1860's. The pétard was a wide-mouthed, cone-shaped mortar that fired miscellaneous ironmongery out of its mouth, a nasty anti-personnel weapon for siege warfare. To be hoist by one's own became proverbial.

The howitzer was intermediate between the cannon and the mortar, intended for long-range fire while elevated at up to 45*, or simply a cannon used when so elevated. Howitzers were also considered as more mobile than cannon. The word comes from the Bohemian for catapult, houfnice, through German. Many of the names of artillery pieces come from earlier mechanical artillery, and some were fanciful. Individual pieces sometimes were given women's names, such as Mons Meg at Edinburgh Castle, made of iron bars and supposed to come from Mons (which is doubtful).

Bombs

In addition to solid spheres of stone, lead, or cast iron, bombs could also be fired from mortars, and later became quite popular, especially as an antipersonnel weapon. They were not usually fired from cannon until later. A bomb was a hollow sphere of cast iron with a port into which a fuze could be hammered. Fuze is a military spelling of fuse, derived from the French fusée, coming from the Latin fusus for a wooden spindle, which the early ones resembled. The largest bombs were about 13 in diameter, 2 in thick, and weighed about 2 cwt, holding a little over 10 lb of powder. They shattered on exploding, sending bits everywhere. Grenades were merely small bombs thrown by hand instead of by a cannon. In England, bombs became known as shells by 1800, the word coming from the German Schale. 5-1/2 in shells were thrown by 24-pdrs, 8 in shells by 68-pdr carronades. The largest shells were thrown by mortars. Hand grenades are, of course, small bombs thrown by hand, and these were used quite early.

Bombs that burst and throw bits of metal are wrongly associated with shrapnel, named after Lt. Henry Shrapnel, RA, who invented a shell containing a charge only large enough to shatter the casing, and which was filled with small projectiles, that would travel on at the original speed of the shell. This kind of shell was first used in 1804.

Shells are said to have been used at the sieges of Naples in 1495 and of Wachtendorf in 1588. Henry VIII is reputed to have had mortars and bombs made by foreigners in 1544, and by 1634 they were in common use by the Dutch and Spanish. Of course, bombs could be as effectively thrown by catapults as by cannon. Incendiary bombs had been known since antiquity.

The fuzes were made of wood, through which a hole was bored to hold the fuse compound, which was specially made to burn slowly (a low-nitrate powder, or cord soaked in saltpetre or wine lees). These early fuses were difficult to use, rather dangerous and too unreliable to be really effective. 'Bombs bursting in air' may have been a common sight, when a fuze was lit too soon or burnt too fast. At the time, such air bursts were considered wasted rounds. They wanted the bomb to roll around a bit on the ground before exploding. Effective bursting bombs had to wait until a reliable time fuze was invented, an example of which was first used effectively at Gibraltar in 1779-83. Fuzes can be classified as percussion, igniting when the projectile hits its target, or concussion, igniting when the projectile is fired.

Infernal Machines

Infernal machine is a good name for the cowardly and dishonourable contraptions intended to poison, burn, maim, torture and kill unsuspecting and often unforeseen victims. They are used by governments, terrorists and other vile forces in pursuit of their cruel aims. Poisons of all kinds and methods of delivery, including infectious diseases, as well as incendiary devices, have been used as infernal machines since the beginning of history, so they certainly did not originate with gunpowder. In fact, chemical and biological agents are still widely used, and are infernal machines when used secretly and randomly against noncombatants. However, gunpowder does make a wide assortment of effective infernal machines easily available. Aerial bombardment comes under this rubric, but is not usually so included. Land mines are indeed infernal machines, and excellent examples of them, since they are concealed and their victims random. As originally used, they were supposed to be laid in clearly marked areas, and charts of the exact location of each mine were to be kept by those who laid them. The idea was to create an obstacle, usually covered by gunfire, that was always removed when the need for it was past. Modern armies being vile and cowardly, this is, of course, no longer done. Booby traps are very popular infernal machines. There is an element of justice in arranging an infernal machine triggered by valuables, as irresistible as a young woman to looting soldiers. The base practice of booby-trapping the bodies of dead soldiers is also practiced. Infernal machines directed against a random soldier are less reprehensible than those directed against random civilians, which constitute the vilest and most cowardly crimes possible.

Recoil

One thing that every cannon does is recoil. If you try to prevent it, the cannon usually smashes your restraint, the more violently the more you try to interfere with its motion. A cannon on a sailing ship recoiled violently in its carriage on the gun deck, until eventually restrained by ropes. One recent television series ('Longitude') correctly showed the violence of this recoil. However, on television one sees a lot of people firing guns, but the guns never recoil. Anyone firing a pistol for the first time is shocked by the kick of the recoil. If you hold the trigger back on an automatic weapon, it simply climbs to fire at the heavens before you know it. Modern soldiers fire one aimed round, and then a half dozen to the sky, with assault rifles. If anyone shoots at you, always duck; chances are their shot will go high. A light gun has an awesome recoil, a heavy one is much easier to control. A revolver recoils strongly, since the whole weapon recoils. The bolt of an automatic pistol recoils inside the weapon, and is brought to a halt by springs, so the recoil is eased somewhat. A field cannon on wheels virtually leaps into the air when fired, and must be restrained by digging in its trail or by ropes. When you see the cannon on television merely belching smoke and shivering, you know they are not firing a ball. When a blank is fired, there is very little recoil. Something still comes out of the muzzle, however, since there has to be a wad. An American preacher recently killed himself impressing his congregation by firing a pistol with a blank load at his head.

Recoil discourages a soldier from firing, and a heavy weapon discourages him from moving, so armies look for light weapons with light recoil, contradictory aims. Bullets can be made lighter, and have decreased in calibre from about 0.702" of the Minie percussion-cap rifle of the mid-19th century, to current figures of 0.26" or less. This makes a very inaccurate, short-distance weapon, but today's soldiers are poor, flinching marksmen anyway. Another means is to cause the weapon to recoil upwards, and most do this as well, especially pistols, spoiling the aim for all but the first shot. As a result, soldiers these days make more noise than anything else.

Gun Carriages

The cannon was originally lashed to a log or pole, or to a flat table, and supported in a rest near the muzzle. In this form, the cannon was not mobile, the recoil was difficult to absorb, and the piece could not be elevated conveniently. To permit elevation, trunnions could be pivoted in two sturdy beams on either side of the cannon, made a single unit by spacers. Elevation was then set by wedges or coigns, or else by a screw. To provide mobility, this assembly was then mounted on a 4-wheel wagon. However, the cannon could not then be easily pointed, and the recoil was still difficult to handle. The answer was found by using only two wheels, with the axle supporting a sturdy trail that accommodated the cannon with its trunnions. Now the cannon could be easily pointed, and the trail could be dug in to absorb the recoil. To move the cannon, the trail was supported by a limber, a light two-wheeled cart with the harness attached, consisting of a pole and swingletrees. Two or four horses was the usual team, though there was an effort to make light cannon that could be moved with a single horse. A swivel cannon is very useful, since it can be pointed quickly to any quarter, but the swivel cannot stand heavy recoil, so the size of a swivel cannon is strictly limited.

Cannons and Physics

A curiosity of television cannon is that you hear the report at exactly the same time as you see the flash, even if the cannon is rather distant. This is indeed remarkable. I recall one news report from the Gulf War showing a bombardment in which the bangs came precisely when a bomb was seen to explode at some distance. The bangs were put in later to amuse the audience. What you see and hear is not always what really was. When you see an artillery battery fire in a television spectacle, you ought to see the flash and smoke in silence, then later the rumbling report. If you were actually in front of a battery firing at you, you may never hear the report at all, since the ball will arrive in advance of it, but you may be able to see the ball as it comes. Balls passing overhead or to the side make a definite and chilling rushing sound.

I think Galileo used cannon to measure the speed of sound; certainly someone did, since it was so obvious. The sound from cannon a mile away is heard some five seconds after one sees the smoke. Nevertheless, early measurements were inaccurate. Count Rumford was astonished by the amount of heat generated by boring a cannon, and measured it with a calorimeter. At the time, it was considered that the heat fluid, caloric, was squeezed out of the metal in boring, but Rumford's experiment seemed to show that it could be created in unlimited amounts, raising serious doubts as to its material nature. Cannon firings were used as time signals, as well as expressions of welcome for VIP's, or when the local team scores.

Projectile motion is a standard exercise in elementary Physics. If V is the muzzle velocity, and E the angle of elevation, the range R = (V2/g) sin 2E, the maximum height reached is H = (R/4) tan E, and the time of flight is T = (2V/g) sin E, where g is the acceleration of gravity, 32.2 ft/sec2, or 9.8 m/s2. This neglects wind resistance, which is not a good assumption for most cannon trajectories, where the muzzle velocity may be close to sonic, and certainly not good enough for accurate firing tables. The calculation of firing tables was one of the first applications of electronic computers in the 1940's. Also, if M is the mass of the cannon, and m the mass of the ball, then the velocity of recoil is v = (m/M)V, from the conservation of momentum. This relation can be used to analyse the ballistic pendulum, a simple apparatus used to determine muzzle velocities, and part of the elementary Physics laboratory.

The ballistic pendulum was invented by Benjamin Robins (1707-1751), an underappreciated English mathematician and writer on ballistics, and was used for the evaluation of the strength of gunpowder and the measurement of air resistance. An account appears in his New Principles of Gunnery (1742). Robins' pendulum was suspended from a tripod, and the bullet was shot into a wooden block screwed to the pendulum. The pendulum weighed 56 lb 3 oz, and it was 52" from its centre of gravity to the support. From the period of free oscillation, the equivalent simple pendulum was 62-2/3" long, and the center of the wood block was 66" from the support. The maximum deflection of the pendulum was measured by the length of ribbon that was pulled out when the pendulum swung. Knowing the maximum deflection of the pendulum and the weight of the bullet, the speed of the bullet can be found. This is explained in Robins' Proposition VIII: "To determine the velocity, which any ball moves with at any distance from the piece, it is discharged from."

In another paper, Robins explains the benefits of rifling, which is the cutting of grooves in the barrel of a gun. At first, these were simply straight grooves, apparently to combat fouling of the barrel, and appeared as early as 1500. Pitched, or spiral, rifling imparts a rotation to the bullet, and it came to be recognised that this caused a truer flight of the projectile. Indeed, the feathers of arrows are slightly canted to cause the arrow to rotate about a longitudinal axis to stabilise its flight. Robins pointed out that the rotation equalised the differences in air resistance due to small irregularities in the bullet. The Germans and Swiss had known about this for some time, he said. The first way of loading a rifled gun was to hammer a slightly oversize bullet down the bore, distorting it into the rifling, but a much more satisfactory way was to use a greasy patch of leather or fustian wrapped around a smaller bullet. Carman thought this was an American invention, used in the Kentucky Rifle (which was actually made in Lancaster, Pennsylvania), but the origin was probably German.

Cannonballs and bullets were always spherical until about 1875. Robins pointed out that the rotation imparted by rifling had a stabilising effect only when the axis of rotation was in the direction of motion. This benefit would be lost in high-angle fire (indeed, mortars are smoothbore even today). He suggested egg-shaped bullets to ensure that the rotation axis would be brought in coincidence with the direction of motion.

Since it was difficult to load a rifled gun from the muzzle, breechloading rifles were a possible alternative. At the time of the American War for Independence, Patrick Ferguson designed such a breechloader, and armed his company of American Volunteers, sharpshooters from New Jersey and New York, with these very effective rifles, to oppose the muzzle-loading Kentucky Rifles of the Continental Army. Ferguson was killed at King's Mountain, South Carolina, a special target because of the effectiveness of his company. The British Army forgot all about him, and did not issue breechloading rifles until 1866.

Small Arms

The earliest firearm was a bamboo tube that shot arrows. After it gave rise to the cannon, a need was felt for a portable weapon that could be carried and fired by an individual soldier. The first was a small cannon on the end of a wooden shaft, held between the arm and the body. The projectiles were usually lead balls, which were easily cast to size. Warfare was revolutionised, since cowards and villains now became useful soldiers, and the rudely trained common man could profitably be sent into the field, in place of the valuable horseman. At first, the use of small arms was deprecated as contrary to the usages of war and chivalry, but the objection did not long last when it was found that the meaner classes did most of the dying. The modern army was born, consisting largely of these lower classes. Infantry, indeed, means 'those who do not speak.' Firearms are most effective when used sneakily from ambush with surprise, and especially against the unarmed and unwary. This has remained the principal theory of the use of firearms, except for the temporary vogue of duelling with pistols, which was courageous stupidity, especially popular with military men. More recently, another advance in warfare has made the killing of a score of civilians face-to-face with a machine gun a war crime, while pressing to death or burning alive hundreds or thousands of unseen noncombatants with bombs from relative safety and comfort merits honours and decorations.

Two hands were required to hold and aim the weapon, so there was not a hand free to apply the match to the touch-hole. This problem was solved by moving the touch-hole from the top to one side, and providing a shallow pan there to hold a priming charge. The match was clamped in a pivoted holder called variously a dragon, dog, cock or serpentine, and was brought down to the priming pan by pulling a trigger. This arrangement was called a matchlock, and the weapon a harquebus, or German hackbüchse. The long barrel was supported by a rest, and sometimes had a hook beneath it to absorb recoil (from which its name derives) or a curved stock. This was the ancestor of the musket, first seen in Italy around 1530, with a 4-foot barrel, and firing bullets of 12 to the pound. The origin of the word musket is not known. These bullets could pierce armour.

The lack of standardisation of the calibre of muskets made the supply of large units difficult, so light muskets were made of a standard calibre, and these weapons came to be called calivers, the characteristic weapon of a common infantryman in Elizabethan times. The barrel was slightly shorter, and they were not used with a rest. Their balls could not pierce armour. Even calivers were inconvenient for the cavalry, who needed a shorter weapon, and one that could be carried without occupying the hands, which were required for managing the horse. The first such weapon was the petronel, fired against the breast instead of the shoulder, and carried with a sling, across the back. This developed into the dragon, with only a 16" barrel, which gave its name to the mounted infantry, the dragoons. The carbine was developed from the short Moorish musket, with a barrel as short as 24" or even shorter. From the late 17th century, some carbines were rifled, but rifled weapons were harder to clean than smoothbores, and remained relatively rare for some years. The name comes from the Arabic carab, weapon. The fusil was a similar small musket with a sling and a 3-foot barrel, used by dragoons and grenadiers.

The matchlock was cheap and effective, but its light gave away the position of its user at night. The much more expensive wheel-lock held a piece of iron pyrites in jaws against a toothed wheel. This wheel could rotate, driven by a spring that had to be wound up first with a key. When the spring was released, the rotating wheel produced a stream of sparks that ignited the priming charge. Pyrites is not strong, and often crumbled, so a more durable substitute was found in flint. In the flint-lock, the flint holder is snapped against a serrated piece of steel, knocking off glowing sparks into the priming pan. This snaphaunce appeared in the 16th century, and lasted until the introduction of percussion locks in the 19th century (1830). The famous Brown Bess, the flintlock used by Wellington's army at Waterloo in 1815, got its name from its brown colour and the German büchse.

The percussion cap was discovered by Reverend Forsythe and perfected in 1830, although he began his trials in 1805. The search for a safe and convenient way to use the newly discovered fulminates was a long one, and the secret turned out to be to encapsulate the substance between copper foils. A rifle could now be fired simply by allowing a hammer to fall on the cap, and the explosion products would ignite the main charge. This was instantaneous, and there was no smouldering match or stream of sparks to contend with. The caps were originally separate for use with muzzle-loaders, but could be combined with the bullet and powder in a cartridge case for breech-loaders. The final development was the use of a 'needle' instead of a hammer to strike the cap.

Small arms projectiles were always of lead. Lead bullets were easy to cast as needed, which was essential when there was no standardization of calibre. A two-part, hinged bullet mould and a ladle was all that was required, other than a good fire and bars of lead. The bullets could easily be cleaned up with a file or a knife. Antimonical lead, or hard lead, could be used for bullets. The size of bullets was usually stated by giving the number of bullets to a pound of lead. The calibre in inches can be found by dividing 1.67 by the cube root of the number of bullets per pound. The Kentucky Rifle used bullets 16 to 20 to the pound, or calibres of 0.66" to 0.62". In the final days of muzzle-loaders, the ball, powder and wad were all packaged in a paper cartridge for convenience and speed of loading. The soldier ripped off the end of the cartridge with his teeth, poured the powder down the barrel, pushed in the wad and bullet, and rammed it down with his ramrod. The exact procedure would depend on the details of the cartridge and weapon, of course.

Employment of Cannon

Cannon added a new service branch to the field army. Artillery joined cavalry and infantry. It was a shock weapon, most effectively used in mass, and its placement was critical. The battery itself was fixed, but fire could be directed to any point within range very quickly. The battery had to be carefully protected from assault, while its field of fire had to be as open and level as possible. One good volley across the front of a cavalry or infantry charge would lead to incredible destruction. The ammunition could be the solid ball, or for greater effect against men and horses could be replaced by two half-shells joined by a length of chain, or a bag of grapeshot. Grapeshot had a wooden base and a rod perpendicular to it, around which bullets were stacked, all inside a cloth bag. A cannonball heated red hot could be used to start fires. In this case, a damp wad was necessary in front of the usual dry wad. The shell was a hollow shot filled with gunpowder and fitted with a fuze, as described above. The fuze was lighted, and the shell rammed into the gun and fired. In all this activity, the gun was generally pointed level or only slightly elevated. The battery could protect itself fairly well against a frontal assault by firing directly into the enemy. It was most vulnerable to a cavalry attack from the rear, when its powerful weapons would be of no avail. Cannon rendered fortresses and castles mere temporary protection.

A completely different tactic was the artillery duel, or counter-battery fire. The muzzles would be elevated for long range, and the fire directed on an enemy battery, which might reply in kind. Observation of the fire could correct the aim of the cannon for maximum effect. Before the age of electrical communication, only targets that could be seen from the battery, or from a nearby hill, could be attacked by observed fire. Where cannon fire could not be observed, it was generally ineffective, so elevated cannons were not a common sight until later days, when observers could use telephones for spotting.

Cannon quickly became indispensable for naval warfare. Closing with and boarding an enemy ship became the final stage of the battle, not its beginning. The preliminary stages were manoeuvre to gain advantage, bombardment of the enemy ship to destroy its masts and rigging, and so its ability to manoeuvre, to sweep its weather decks of defenders, and to stave in its wooden sides and set it on fire. Fire was set by heating the shot red-hot in a furnace and lodging it in the enemy's flanks. The engagement did not begin at full range of the cannon, but usually at 'half pistol shot' or about 100 yards, frighteningly close, when the broadsides would have their maximum effect. Naval warfare was extremely unpleasant for the sailor.

The heaviest guns were placed on the main gun deck, low in the ship. Lighter guns were placed on higher decks, and even on the top deck. Ships with several gun decks tended to be top-heavy and in danger of capsizing if the weight carried was not properly distributed. These guns fired broadside, so the ship had to be manoeuvred to direct their fire. Guns on the weather deck could be aimed more flexibly, and the cannon placed at the bows and the stern were especially valuable to protect the ship from attack from these directions, which were favoured by attackers since they were not then exposed to the ship's broadside. It was found that ships of greater armament (weight of broadside), competently handled, could always defeat a ship of lighter armament, but that the more lightly armed ships, if competently designed, could always outrun a more heavily armed ship. When two ships encountered one another, their captains carefully considered their chances, so the result was that nearly all individual battles were between ships of about the same size. Slow lightly armed ships did not survive long in warfare. Fleet battles were something completely different, where manoeuvre, control and the weather were the determining factors. More information on naval warfare with cannon around 1812 can be found in Naval Warfare in the Age of Sail, which includes some photographs of cannon and a discussion of the different types used on ships.

HMS Warrior, the large iron steam frigate launched in 1860 and now exhibited in Portsmouth, was furnished with a broadside of 68-pounders at the blockheaded insistence of the Admiralty, who could not conceive of a ship without such armament. These cannon were, in fact, totally useless to this ship and were even a disadvantage, since they got in the way, represented unnecessary weight, and required gun ports that weakened the ship. The Armstrong breechloading rifles on the deck would have been quite sufficient armament, since they outranged all other naval guns, and were devastatingly effective. Warrior's iron and teak armour was proof against any contemporary attack, as well, so it could simply ram lesser ships. Warrior, which could have sunk all the navies of all the world single-handed for a few years, never fired its guns in anger.

A descendant of the smoothbore cannon, the trench mortar, was found to make a very useful infantry weapon, perhaps as late as the First World War. This was a light weapon consisting of a relatively thin tube with a base plate, and a means to hold and adjust the elevation of the tube. The ammunition was a small bomb with stabilizing fins to which the charge of powder was attached in the form of several small bags, the desired number of which would be used as the charge. The detonator in the centre struck a firing pin at the base of the tube when the mortar round was dropped inside, and the explosion would loft the round into the air on a high trajectory. In the U. S. Army, the smallest of these was 60 mm caliber, and could easily be carried and served by two men. This gave even small units their own artillery, which could be very effective, especially when a modest battery of them could be formed by pooling company resources. These mortars were very effectively used to cover obstacles, such as barbed wire, when previously fired so that it was known that the rounds would fall exactly on the obstacle when needed. Later, the planning and skill required seemed to exceed the capacities of the soldiers, so the small mortar was discontinued. Larger mortars, 80 mm and 4.5 inches (114 mm; at first called a chemical mortar because its original purpose was to launch shells of phosphorus or poison gas) were equivalent to real artillery, and were very effective when properly used. Together with the rocket launcher and recoilless rifle, mortars formed a new light artillery that was much easier to move and use than traditional artillery, and formed an integral part of the infantry unit.

References

Information on 18th century and early 19th century practice came from Diderot's Encyclopédie (1763) and Rees' Cyclopaedia (1819), passim. J. R. Partington, A History of Greek Fire and Gunpowder (Baltimore: Johns Hopkins, 1999) is authoritative on the origins of gunpowder. B. H. St.J. O'Neil, Castles and Cannon (Oxford: The Clarendon Press, 1960) has information on medieval British castles and cannon, with a few illustrations of early cannon. Louis Napoleon's (Napoleon III) Études sur le Passé et l'Avenir de l'Artillerie (1862, reprinted 1974), William Y. Carman A History of Firearms to 1914 (1955). Robins' ballistic pendulum is described in James Wilson, Mathematical Tracts of the Late Benjamin Robins Esq. FRS (1761). [Robins came from a quaker family of Bath. The quakers did not esteem mathematics or science, but his gifts were recognised by others who fostered his abilities. His first paper, on Newton's fluxions, was published in the Philisophical Transactions in 1727. Robins' work is good evidence of the revolution in Physics ignited by Newton.] Baxter and Johnson's Medieval Latin Word List was also consulted. The literature of the subject is huge, and the bibliography in Partington should be consulted for more information. I only list here the references that I consulted directly for this paper.

Composed by J. B. Calvert

Created January 2000

Last revised 28 January 2000