The Pyrotechnic Section was composed of a number of units, each with its own problem. The gas shell was studied, with special reference to the stability of gases and toxic solids, both on storage and on detonation. Extensive work was carried out on smoke screens—a Navy funnel, an Army portable smoke apparatus, using silicon tetrachloride, a grenade, a Livens, and various shell being developed for that purpose. The smoke screen was adapted to the tank and the airplane as well as to the funnel of a ship. Several types of incendiary bombs and darts were perfected. The liquid fire gun was studied but the results were never utilized because of the abandonment as useless of that form of warfare. Various forms of signal lights, flares, rockets and colored smokes were studied and in most cases specifications were written. Extensive studies were also carried out on gas shell linings, from which a lead and an enamel lining were evolved. Many physical properties of war gases and their mixtures were determined. The Dispersoid Section studied the production of smokes or mists from various solid and liquid substances. Apparatus were developed to study the concentration of smoke clouds and their rate of settling. The efficiency of various filters and canisters was determined, and among other things, a new smoke candle was perfected. Mechanical research at first was related to design and construction of a canister and mask, based on the English type. During the latter part of 1917 the Tissot type of mask was studied and then turned over to the Gas Defense Division. A Navy Head Mask and canister was perfected. The horse mask was developed along the lines of the British type, and also a dog mask of the same general nature. Horse boots were also constructed, though they never were used at the front. Many Ordnance and Pyrotechnic problems were also successfully completed, not the least of which was a noiseless gas cylinder. This section developed the first special poison gas suit, composed of an oilcloth suit, a mask and helmet and a special canister. The Manufacturing Development Section had general charge of the defense problems, and really acted as an emergency section, filling in as occasion demanded. They developed mustard gas clothing and a horse mask. They constructed a hydrogen plant at Langley Field, assisted in solving the difficulties relating to Batchite charcoal at Springfield, Mass., and co-operated in the study of paper and felt as filtering materials for smokes. Towards the close of the war the Section was interested in the application of the gas mask to the industries. The Physiological work is discussed under the Medical Division.