The war in the air put added demands upon ordnance. It required the stripped machine gun firing cartridges so rapidly that their explosions merged into a single continuous roar, yet each shot so nicely timed that it passed between the flying blades of the propeller. There had to be electric heaters for the gun mechanisms to prevent the oil which lubricated them from becoming congealed in the cold of high altitudes. The airplane guns required armor-piercing bullets for use against armored planes, incendiary bullets to ignite the hydrogen of the enemy's balloon or to fire the gasoline escaping through the wound in the hostile airplane's fuel tank, and tracer bullets to direct the aim of the aerial gunner. Other equipment for the airman included shot counters, to tell him instantly what quantity of ammunition he had on hand, and gun sights, ingeniously contrived to correct his aim automatically for the relative speed and direction of the opposing plane. These were all developments in ordnance brought about by the great war, and in each case they involved problems for the production organization to solve. Then there were the drop bombs of aerial warfare, of many gradations in weight up to 500 pounds each, these latter experimental ones forecasting the day when bombs weighing 1,600 pounds would be dropped from the sky; then bomb sights to determine the moment when the missile must be dropped in order to hit its target, sights which corrected for the altitude, the wind resistance, and the rate of speed of the airplane; and then mechanisms to suspend the bombs from the plane and to release them at the will of the operator. The list might be stretched out almost indefinitely--through pyrotechnics, developed by the exigencies in Europe into an elaborate system; through helmets and armor, revivals from medieval times to protect the modern soldier from injury; through the assortment of heavy textiles, which gave the troops their belts, their bandoleers, their haversacks, and their holsters; through canteens, cutlery for the mess in the fields, shotguns, and so on, until there might be set down thousands of items of the list which we know as modern ordnance. It will be noted that the most important articles in this range are articles of a noncommercial type. In other words, they are not the sort of things that the industry of the country builds in time of peace, nor learns how to build. Many other war functions came naturally to a country skilled in handling food supplies for teeming populations, in solving housing problems for whole cities, and in managing transportation for a hundred million people; there was at hand the requisite ability to conduct war enterprises of such character smoothly and efficiently. Yet there was in the country at the outbreak of war little knowledge of the technique of ordnance production.