Incendiary Devices

The incendiary devices used during the late war included: bombs, shell, tracer shell and bullets, grenades, and flame throwers.

Bombs

Incendiary bombs were used almost exclusively by aircraft. The value of bombs which would cause destruction by starting conflagrations was early recognized but their development was rather slow. While the designs were constantly changing, two stand out as the most favored: a small unit, such as the Baby Incendiary Bomb of the English, and a large bomb, such as the French Chenard bomb or the American Mark II bomb.

In general bombs which, when they function upon impact, scatter small burning units over a considerable area, are not favored. Small unit bombs can be more effectively used because the scatter can be better regulated and the incendiary units can be more advantageously placed.

German Bombs. Incendiary bombs were used by the Germans in their airplane raids, usually in connection with high explosive bombs. A typical armament of the later series of German naval airships consisted of the following:

2	660-pound bombs
10	220-pound bombs
15	110-pound bombs
20	Incendiary bombs

making a total weight of about 2½ tons.

Fig. 107.—Incendiary Devices.

(From Left to Right).
Mark II Bomb, B. I. Bomb, Mark I Dart, Mark II Dart,
Mark I Dart, Grenade, Mark I Bomb.

A typical German bomb is shown in [Fig. 108]. It consists essentially of a receiver of white iron (R) composed of a casing and a central tube of zinc, joined together in such a fashion that, when the whole was complete, it had the appearance of an elongated vessel with a hollow center. Within this central hollow is placed a priming tube (T) of thin sheet iron, pierced by a number of circular openings. The receiver is about 445 mm. (17.5 in.) high and 110 mm. (4.3 in.) at its maximum diameter. It is wrapped with strands of tarred cord over nearly its entire length. The empennage (270 mm. or 10.6 in.—in height) consisted of three inclined balancing fins, which assured the rotation of the projectile during its fall.

In the body of the bomb was a viscous mass of benzine hydrocarbons, while the lower part of the receiver contained a mixture of potassium perchlorate and paraffin. The central tube apparently contained a mixture of aluminum and sulfur.

Fig. 108.—Aerial Incendiary Bomb,
November, 1916.

Fig. 109.—German Incendiary Bomb,
Scatter Type.

All dimensions in millimeters.

Later the Germans used a scatter type of bomb ([Fig. 109]) which was designed to give 46 points of conflagration. Each of these 46 small cylinders contained 50 grams of an air incendiary material. They were arranged in layers, packed in with very fine gun powder. The bomb is ignited by a friction lighter which is pulled automatically when the bomb is released from the aeroplane. The bomb is constructed to burst in the air and not on striking the ground. The upper part of the projectile consists of a cast iron nose riveted to the sheet iron body of the bomb. When the explosion occurs, the nose is blown away and the small incendiary cylinders are scattered in the air.

The incendiary material appears to be a mixture of barium nitrate and tar. Its incendiary power is very low because combustion takes the form of a small flame of very short duration. It should, however, be very valuable for firing inflammable materials.

British Bombs. The early British bombs were petrol bombs, which were used without great success for crop burning. Phosphorus bombs were then used for attacking aircraft. But the most successful incendiary is the so-called “Baby Incendiary Bomb.” This is a 6.5-ounce bomb with an incendiary charge of special thermit. These small bombs are carried in containers holding either 144 or 272 bombs. The former container approximates in size and weight one 50-pound H.E. bomb and the latter one 120-pound H.E. bomb. The bomb contains a cartridge very much like a shot gun shell which, on impact, sets down on the striker point in the base of the body, and causes the ignition of the charge. It is claimed that the cartridge of the B.I. bomb burns when totally immersed in any liquid (water included) and in depths up to two feet the flame breaks through the surface.

French Bombs. The French used three types of incendiary bombs, a special thermit (calonite), the Chenard and the Davidsen. The Chenard bomb is a true intensive type and is thought to be very successful. It functions by means of a time fuse operated by the unscrewing of a propeller, before striking the ground, and reaches its target in flames. Its chief disadvantage is the small amount of incendiary material which it carries. The Davidsen bomb expels its charge as a single unit and is not considered as valuable or as successful as the Chenard.

American Bombs. The program of the Chemical Warfare Service included three types of bombs:

Mark II	Incendiary drop bomb
Mark III	Incendiary drop bomb
Mark I	Scatter bomb

Mark II Bomb. The incendiary Mark II drop bomb is designed to be dropped from an aeroplane and is intended for use against buildings, etc., when penetrating effect followed by an intensive incendiary action is sought.

The bomb case consists of two parts: a body and a nose. The body is a tapering zinc shell which carries the firing mechanism and stabilizing tail fin at the small end and at the large end a threaded ring which screws into the nose. The nose is of drawn steel of such shape as to have low end-on resistance and is sufficiently strong to penetrate frame structures.

Fig. 110.—Loading Bombs with “Solid” Oil.

The incendiary effect is produced by a thermit charge carried in the nose of the bomb. This charge is ignited by a booster of “Thermit Igniter” fired by black powder. The latter is ignited by a flash from the discharge of a standard 0.30 caliber service cartridge contained in the body of the bomb, and exploded by a firing mechanism of the impact type. This method of firing has proven wholly unsatisfactory and will be superseded by some more direct-acting mechanism. The body of the bomb is filled with solidified oil. The molten thermit burns through the case of the bomb and liberates the oil which has been partially liquefied by the heat of the thermit reaction. Additional incendiary effect is afforded by the sodium nitrate contained in the nose below the thermit, and by two sheet lead cylinders filled with sodium and imbedded in the solid oil. The sodium increases the difficulty of extinguishing the fire with water.

Mark III Bomb. This bomb is simply a larger size of the Mark II bomb, its weight being approximately 100 pounds as compared with 40 pounds for the Mark II bomb. It is designed to be dropped from an aeroplane and is intended for use against buildings when marked penetrating effect is desired. The method of functioning is the same as the Mark II bomb and it has the same defects in the firing mechanism.

Mark I Bomb (Scatter Type). The Mark I incendiary drop bomb is also designed to be dropped from aeroplanes and is intended for use against grain fields, ammunition dumps, light structures or similar objectives when only a low degree of ignition is required. It is of the so-called scatter type, due to the action of the exploding charge which casts out incendiary material within a radius of 20 feet from the point of contact.

The incendiary action is due to the ejection of the various incendiary units in the bomb by the explosion of the black powder in the nose. The flash of this explosion serves to ignite the units. A powder charge in the rear of the bomb acts simultaneously with the nose charge, opening the bomb casing, and aiding materially in the scatter of the units. The bomb is so arranged as to function close to the ground, which is a further factor in the scatter of the units.

The incendiary units are waste balls about 2.5 in. in diameter and having an average weight of 2.5 ounces, tied securely with strong twine. These are soaked in a special oil mixture. Carbon disulfide and crude turpentine, or carbon disulfide, benzene heads and crude kerosene gave satisfactory results. A later development attempted to replace the waste balls by solid oil, but the difficulties of manufacture and questions of transportation argued against its adoption.

These bombs were not used at the front. Nearly all of the American incendiary bombs proved too light on the nose and lower half, generally resulting in deformation upon impact and very poor results. New ones will be made stronger.

Incendiary Darts

The British early recognized the value of a small bomb, and consequently adopted their B.I.B. (Baby Incendiary Bomb), weighing about 6.5 ounces. These are capable of being dropped in lots of 100 or more and thus literally shower a given territory with fire. The intensity of fire at any given point is much less than that obtained with the larger bombs, but the increased area under bombardment more than counter balances this disadvantage. While the British aimed at the perfection of a universal bomb, the American service felt that two classes should be developed, one to be used against grain fields and forests, the other against buildings.

The first class was called the Mark I Dart. This consisted of an elongated 12-gauge shot gun shell, filled with incendiary material and provided with a firing mechanism to ignite the primer as the dart strikes the ground. The flash of the primer sets fire to the booster, which, in turn, ignites the main incendiary charge. The latter burns several minutes, with a long flame. A retarding stabilizer attached to the tail of the dart serves the two-fold purpose of insuring the functioning of the firing mechanism and, by retarding the final velocity of the dart, preventing the collapse of the dart body when dropped from very high altitudes.

The incendiary mixture is one which gives a long hot flame, burns for several minutes and leaves very little ash. In general it consists of an oxidizing agent (barium or sodium chlorate), a reducing agent (aluminum, or a mixture of iron, aluminum and magnesium), a filler (rosin, powdered asphaltum or naphthalene) and in some cases a binder (asphaltum, varnish or boiled linseed oil).

The Mark II Dart was developed to furnish a small size penetrating agent. It consists of a two-inch (diameter) zinc case filled with thermit and solid oil as the incendiary materials and provided with a cast iron nose for penetration. During the first half minute after firing, a pool of molten iron is formed by the thermit, which is very penetrating and affords a good combustible surface for the oil, which burns for an additional ten minutes.

It has an advantage over the Mark I dart in that it penetrates, and over the Mark II bomb in that it is smaller and lighter in weight.

Incendiary Shell

Incendiary shell have been successfully used against aircraft and to some extent in bombardments of inflammable ground targets. Anti-aircraft shell are of small caliber and are usually tracer-incendiary. Such shell are filled with pyrotechnic mixtures which ignite at the moment of firing, or by time fuse, and are effective against highly inflammable material. Shell filled with thermit which explode and scatter the molten iron have been used against aircraft and ground targets, but with rather poor results. Large shell, which burst upon impact and scatter units of burning materials, have been used with some success against ground targets.

Tracer shell contain such mixtures as barium nitrate, magnesium and shellac, or red lead and magnesium.

Incendiary Bullets

Incendiary bullets are only effective against highly inflammable material, and are therefore used principally in aerial warfare against aircraft, either for the purpose of igniting the hydrogen of the gas bag, or the gasoline. The present tendency is towards the use of the large size (11 mm.) bullet, because of its greater incendiary action.

The incendiary material is either white phosphorus or a special incendiary mixture consisting of an oxidizing agent and some combustible or mixture of combustibles. The white tracer bullet contains a mixture of barium peroxide and magnesium. A red bullet contained in addition, strontium nitrate and chloride, or peroxide.

Incendiary Hand Grenade

While the use of incendiary grenades and other small incendiary devices is limited, such armament is considered very valuable in trench warfare. They can be used to set fire to inflammable material, either in offensive or defensive operations.

Phosphorus grenades, while used principally for producing smoke ([see page 302]), have considerable value as an incendiary weapon.

Thermit grenades are very useful in rendering unserviceable guns and other metallic equipment which must be abandoned. They permit aviators to destroy planes which motor troubles oblige to land in enemy territory. They are also used to ignite inflammable liquids, thrown into a dugout, or sprayed over an objective by a flame projector.

The Mark I hand grenade was developed for burning enemy ammunition dumps, for clearing away brush or other material in front of trenches and for use in dugouts. The standard H.E. grenade body was half-filled with thermit and half with a celluloid container filled with a solidified fuel oil. The grenade is fired by the spit of the fuse of the bouchon firing mechanism. This, through the booster, lights the thermit igniter, which in turn fires the main charge of thermit. The resulting molten iron readily penetrates the grenade case, at the same time igniting the celluloid case and its contents. The oil burns for about 3.5 minutes. This grenade was never used since it was considered that an all thermit grenade would be of more value.

Trench Mortar Equipment

Special projectiles were designed for use with the Stokes mortar and the Livens’ projector. Thermit was used only in Stokes’ projectiles. The Livens’ projectile was filled with inflammable units (chlorated jute) immersed in a light oil mixture. Thrown from a projector into the enemy’s trench, it explodes, giving a large flash and scattering the burning units over an area of forty yards. The Mark II projectile, designed for general incendiary effect against readily inflammable material, consists of an altered 8-inch Livens’ gas projectile filled with chlorated jute units impregnated with solid oil and immersed in a spontaneously inflammable oil. After a short delay, these units burst into flame and burn vigorously for several minutes. It is almost impossible to extinguish them without large quantities of water. Such bombs have only a very limited use, so that it is questionable if they are really worth while.

Fig. 111.—German 8"
Incendiary Bullet.

Fig. 112.—German Incendiary
Blue Pencil.

German Blue Pencil

A very interesting and curious device was developed by the Germans in the form of an incendiary pencil. Similar in appearance to a common blue pencil, sharpened at one end, they are distinguished only by a small, almost imperceptible, point placed on the outside 11 mm. from the unsharpened end. They are 175 mm. long, 11.1 mm. in diameter and weigh 12 to 13 grams. The interior of the pencil contains a glass bulb, with two compartments filled with sulfuric acid and a celluloid tube filled with potassium chlorate. The glass bulb ends in a slender point; when this is broken the acid comes into contact with the chlorate and causes an explosion. The two materials are separated by a layer of clay, which causes a delayed action of about 30 minutes. The operator breaks the point of bulb, buries the pencil vertically in the inflammable material and then has half an hour in which to get away, before any possibility of a fire. He cuts the pencil with a knife 2 cm. from the point, so that if caught he has the appearance of simply sharpening a pencil.

Flaming Gun

Among the unsuccessful weapons of the late war, the liquid fire gun or Flammenwerfer, as the German called it, is probably the most interesting. Its origin, according to a German story, was due to a mere accident. A certain officer, during peace maneuvers, was ordered to hold a fort at all cost. During the sham fight, having employed all the means at his disposal, he finally called out the fire brigade and directed streams of water upon the attacking force. Afterwards, during the criticism of the operations in the presence of the Kaiser, he claimed that he had subjected the attackers to streams of burning oil. The Kaiser immediately inquired whether such a thing would be possible, and was assured that it was entirely feasible.

Fig. 113.—Liquid Fire Attack.

Long series of experiments were necessary before a satisfactory combination of oils was produced, which could be projected as a flame on the enemy, but they were finally successful. Unlike the use of poison gas, however, the flaming liquid gun did not prove to be a successful weapon of warfare. True, at first they were rather successful, but this was before the men learned their real nature. In the first attack, the Allies were completely surprised and the troops were routed by the flames. Auld tells of one of the early attacks (July 29, 1915) when, without warning, the front line troops were enveloped in flames. Where the flames came from could not be seen. All that the men knew was that they seemed surrounded by fierce, curling flames, which were accompanied by a loud roaring noise, and dense clouds of black smoke. Here and there a big blob of burning oil would fall into a trench or saphead. Shouts and yells rent the air as individual men, rising up in the trenches or attempting to move in the open, felt the force of the flames. The only way to safety appeared to be to the rear. This direction the men that were left took. For a short space the flames pursued them and the local retirement became a local rout. After the bombardment which followed, only one man is known to have returned.

After a study of the pictures of the liquid fire gun in operation, it is evident that the men could not be blamed for this retirement. One has only to imagine being faced by a spread of flame similar to that used for the oil burners under the largest boiler, but with a jet nearly 60 feet in length and capable of being sprayed round as one might spray water with a fire hose.

Later, when the device was better known it was different, though even then it was a pretty good test of a man’s nerve. It was found that the flames could not follow one to the bottom of a trench as the gas did, and that, if a man crouched to the bottom of his trench, his head might be very warm for a minute or so but that the danger was soon past and he then could pick off the man who had so recently made things uncomfortable for him.

While it is said that Major R., who invented the Flammenwerfer, enjoyed a great popularity among his men, and is familiarly known as the Prince of Hades, there is no doubt that this was not shared by the Allies. Their rule was: “Shoot the man carrying the apparatus before he gets in his shot, if possible. If this cannot be done, take cover from the flames and shoot him afterwards.”

The German had several types, which may be grouped into the small or portable and the large Flammenwerfers.

The portable Flammenwerfer consisted of a sheet steel cylinder of two compartments, one to hold compressed nitrogen, the other to hold the oil. The nitrogen furnished the pressure which forces the oil out through the flexible tube. Air cannot be used, because the oxygen would form an explosive mixture with the vapors of the oil, and any heating on compression, or back flash from the flame or fuse might make things very unpleasant for the operator. A pressure of about 23 atmospheres is reached when the cylinder is charged. The nitrogen appeared to be carried on the field in large containers and the flame projectors actually charged in the trenches.

The oil used in the flame projectors varied from time to time, but always contained a mixture of light or easily volatile and heavy and less volatile fractions of petroleum or mineral oil, very carefully mixed. In some cases even ordinary commercial ether has been found in the cylinders.

Fig. 114.—Small Flammenwerfer.

The most interesting part about the flame projector is the lighting device. This is so made that the oil ignites spontaneously the minute the jet is turned on, and is kept alight by a fiercely burning mixture which lasts throughout the discharge. This mixture is composed of barium nitrate, potassium nitrate, metallic magnesium and charcoal, with some resinous material. The priming consists of black powder and metallic magnesium.

When the oil rushes out of the jet, it forces up the plunger of a friction lighter and ignites this core of fiercely burning mixture.

The range of these small projectors is from 14 to 17 meters (17 to 20 yards) but the duration of the flame is rather less than a minute.

In a later pattern, it was designed that one nozzle should be issued to three reservoirs. After the discharge of one, the jet is attached to the others in succession. This is called the “Wx” Flammenwerfer (interchangeable). In this way a squad of three men could carry 58 pints of inflammable oil. It is a question, though, whether the third man would live to use his reservoir.

Fig. 115.—Boyd Flame Projector.

The fact that the trenches were often very close together during the early part of the war, made possible the use of large or stationary Flammenwerfer. These consisted of a steel reservoir 3⅓ feet in height and 1⅔ feet in diameter, weighing about 250 pounds, which could be connected to two steel cylinders, containing nitrogen under pressure. These carried 180 liters (40 gallons) of liquid and operated under a pressure of 15 atmospheres. The discharge nozzle was at the end of a metal tube three feet long, and its orifice was about ⁵/₁₆ of an inch in diameter. The range of this apparatus was from 33 to 40 yards and the duration of the flame from one to two minutes. Because of the comparatively short range of these guns and the ease with which they could be destroyed, if located by the enemy, their use was very limited.

Even with the portable flammenwerfer, the most difficult thing to do is to get near enough the target to make the shoot effective. Another serious disadvantage is its very short duration. It is impossible to charge up again on the spot, and the result is that once the flame stops, the whole game is finished and the operators are at the mercy of the enemy.

With these facts in mind it is easy to see how service in the flaming gun regiments is apparently a form of punishment. Men convicted of offenses in other regiments were transferred either for a time or permanently and were forced under threat of death in the most hazardous enterprises and to carry out the most dangerous work. Taken all in all the flame thrower was one of the greatest failures among the many promising devices tried out on a large scale in the war.

CHAPTER XXI
THE PHARMACOLOGY OF WAR GASES

The pharmacology of war gases plays such an important part in chemical warfare that a brief discussion may well be given of the methods used in the testing of gases for toxicity and other pharmacological properties.

War gases may be divided into two groups: persistent and non-persistent, each of which may include several classes:

I.	Lethal
II.	Lachrymatory
III.	Sternutatory
IV.	Special

Each class necessitates special tests in order to determine whether or not it is suitable for further development.