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78 matter, especially with the long-range heavy flamethrowers, and surprise effect which, in the opinion of some, is the principal if not the only asset of the weapon is entirely lost. The other method is to fix an igniter to the nozzle; this fires the jet at the outset, en- sures surprise and moral effect, for the liquid-fire jet, with its roar, its heat, and heavy smoke intermingled with darting masses of flame, is a terrifying thing. On the other hand nozzle-ignition presents very difficult problems which have never been satisfactorily solved, and the actual burning effect is more local than is the case with the simpler method. On the whole nozzle ignition is to be pre- ferred whenever a reasonably certain ignition device is available. The French made use of both methods, the Germans and British exclusively, or almost exclusively, of nozzle ignition. It was at one time supposed that the unignited jet ranged farther than the flaming jet, but this is not proved. French experiments indicate that what is lost in " sectional density " by igniting the jet is regained by the fact that the surrounding air, heated to a high temperature, offers a lessened resistance.

Ignition devices may be simple portfires (or even petrol-soaked wads) attached by hand to the nozzle and ignited before aim is taken, or more elaborate electrical and mechanical devices. In all cases they are required to ignite, not the oil itself, which emerges in too rigid a column to respond to the spark, but the film of petrol vapour which forms round the column. The spark must be emitted by the igniter as close as possible to the emerging jet without actually touching it. Moreover it must be protected against the wind. Further, the igniter must remain alight and in the correct position during the duration of the throw; this condition is very difficult to satisfy in the case of portable flamethrowers which operate by a succession of short, sharp jets controlled by a trigger, save by the clumsy expedient of a long-burning portfire. Amongst the many forms of ignition three may be specially mentioned :

(a) A British pattern in which two sparking-plugs were mounted in a cup containing petrol, and fired by a magneto generator.

(6) A French type, giving the very long burning required for the successive shots of the portable flamethrowers by means of a tubular magazine fixed to the nozzle. In this magazine was a long stick of alumino-thermic composition, which was continually urged forward by a spring as its head burned away. Primary ignition of the portfire itself was by means of a cerium-steel "briquet."

Fastener*

eedle

and

Cardboard Disc

Striker Pellet

Spring Competition

Piston

Hozzli

FIG. I.

(c) The German service igniter (fig. i), which was very ingeniously devised and was based on inertia. It was a double-walled cylinder attached to the nozzle-tube. The space between the inner and outer walls was filled with an alumino-tnermic composition, open to the air at the top. Inside the hollow of the cylinder and in prolongation of the bore of the nozzle-tube were a piston, a spring, a striker- needle mounted on a pellet, and a cap with powder-relay. Between the cap and the striker-needle was a fixed disc of cardboard. On release the sudden impact of the iet on the piston compressed the spring and the striker against the cardboard disc, then after a moment the needle penetrated this disc, and the spring, decompress- ing itself, forced it on to the cap and so fired the powder relay that

ignited the composition. The attachments which secured the striker, etc., in the bore of the cylinder were instantly burned through, and the jet, blowing out these obstructions, issued and was ignited by the burning composition as it emerged.

The types of flamethrower designed by the three belligerents were classified broadly as heavy, medium or semi-portable, and portable. Those of the heavy class, built for range, all required fixed installa- tions; medium types were simply smaller editions of the heavy types, kept down in weight so as to be able to follow up an advance without undue difficulty; while the portable weapons were without exception designed for use in the course of the attack itself, and especially for the " mopping-up " of captured trenches and for securing the flanks of a line of trenches during " consolidation." In reality, therefore, there are only two types, the heavy and the light, and these are technically very different.

Heavy Flamethrowers. Of the various types of heavy flame- thrower which were evolved in the war, the British show both the best ranging power and also perhaps the greatest variety, this latter being due to the fact that, officially, they never passed beyond the experimental stage into that of a " service store."

The first model to be tried was that designed by an American, Joseph Menchen, which was put before the War Office in March 1915. This was a very large apparatus, several containers being coupled up in series to a single pipe and nozzle, the latter being aimed from under cover by means of power derived from a by- pass on the air bottle (a complication subsequently abandoned). The intention of the branch of the War Office concerned (which subsequently became the Trench Warfare Department of the Ministry of Munitions) was to employ the apparatus not in trenches, for which it was evidently too cumbrous, but to mount it in a large armoured vehicle of the caterpillar class. Such a vehicle was built, concurrently with the first tanks but on a larger scale so as to be able to carry a big supply of oil for the flamethrower, which in the Menchen design had a range of 100 yards. This idea of the flamethrower-tank was, however, al- lowed to drop owing to a variety of causes, of which the principal were the dislike of the British G.H.Q. in France for flame- throwers generally, and the concentration of caterpillar-building resources at home on the gun-carrying tank. Experiment pro- ceeded therefore on heavy types intended for trench warfare, and greater lightness and simplicity than was possible with the Menchen design was aimed at. Later in 1915 the Department produced a heavy flamethrower " battery " which embodied many of the features of the Menchen, and some of those of the Hersent apparatus which had been evolved in France. This " battery " is typical of the normal heavy flame-thrower.

The " battery " (fig. 2) consisted of four vertical cylinders 16 in. in diameter and 48 in. high; on the top of each cylinder was a valve (controlled at first by a wheel and later by special mechanism) which was attached to a siphon tube in the interior of the container. The four valves were connected up in series by short lengths of flexible metallic tubing. The container communicated by a length of flex- ible tube with a rigid tube terminating in a nozzle; this discharge tube was mounted in the trench parapet behind a shield in such a way that the jet could be delivered in any direction and with any eleva- tion. In the final container valve i.e. that leading to the de- livery piping was mounted a trigger valve. On each container was strapped a gas bottle (compressed air, later nitrogen) containing 60 cub. ft. of gas compressed to 1, 800 Ib. per sq. inch. Between