=Hanlon (Experimental) Field.= As early as December 15, 1917, it was decided that an experimental field in France was necessary, and a letter was written to the General Staff requesting authority to establish one. After considerable delay the authority was granted and search for a site begun. This was no easy task. While the French were loading millions of gas shells at the edge of Paris, they appeared unwilling at first to have us establish a gas experimental field except in abandoned or inaccessible spots. Finally a very good site was found and agreed to by the French some 7 miles south of General Headquarters. Just when we were ready to start work the French discovered that the proposed field included a portion of one of their artillery firing ranges. They then suggested another site within 3 miles of General Headquarters. This was a rather fortunate accident as the site suggested was a better one than at first picked out. The field was roughly rectangular from 7 to 8 miles in length, and 3 to 4 miles in width. The total area was about 20 square miles. The work of this experimental field proved a great success and was rapidly becoming the real center of the Gas Service in France. The old saying that the history of a happy country is very brief applies to this story of the Technical Section of the Gas Service in France. Its work did not begin as early as that of the other sections, and as considerable of it was of a nature that could be put off without immediate fatal effects, the Section was enabled to grow without the very serious drawbacks encountered by other Sections of the Gas Service. Nevertheless its usefulness was very great. Those of the Technical Section either at the experimental field or at the laboratory were charged with the opening of all sorts of known and unknown gas and high explosive shells, fuses and similar things to determine their contents and their poisonous or explosive qualities. This was work of a very technical nature, and at the same time highly dangerous. As stated elsewhere, the determination of the life of the masks became one of the problems which the laboratory was trying to solve. Hundreds of canisters were tested, and hundreds per month would have continued to have been tested throughout the remainder of the war had the war gone into 1919. It was on the Technical Section that devolved the duty of determining at the earliest possible moment the physical properties as well as the physiological effects of any new gas. Also on that Section fell the preliminary reports as to the probable usefulness in war of a new gas whether sent over by the enemy or suggested by our own Technical men, or those of our Allies. This was indeed a task by itself, as it required a wide knowledge of the methods of using gases, methods of manufacturing them, and methods of projecting them on the field of battle.