Shortly after the Civil War broke out, Thaddeus S.C. Lowe, an enthusiastic American aËronaut, conceived the idea of sending up scout balloons to reconnoiter the position of the enemy. These balloons were to be connected by telegraph wires with the ground, so that they could direct the artillery fire. The idea was so novel to the military authorities of that day that it was not received with favor. Balloons were looked upon as freak inventions, entirely impracticable for the stern realities of war; and as for telegraphing from a balloon, no one had ever done that before. But this enthusiast was not to be daunted, and he made a direct appeal to President Lincoln, offering to prove the practicability of this means of scouting. So he took his balloon to Washington and made an ascent from the grounds of the Smithsonian Institution, while On one occasion a young German military attachÉ begged the privilege of making an ascent in the balloon. Permission was given and when the German officer returned to earth he was wildly enthusiastic in praise of this aËrial observation post. He had had a splendid view of the enemy and could watch operations through his field-glasses which were of utmost importance. Realizing the military value of the aircraft, he returned to Germany and urged military authorities to provide themselves with captive balloons. This young officer was Count THE WEIGHT OF HYDROGENBefore we describe the Zeppelin airships and the means by which they were eventually overcome, we must know something about the principles of balloons. Every one knows that balloons are kept up in the air by means of a very light gas, but somehow the general public fails to understand why the gas should hold it up. Since the hydrogen is sixteen times lighter than air, naturally it will float in the air, just as a piece of wood will float in water because it is lighter than the same volume of water. If we surrounded the thousand cubic feet of hydrogen with a bag so that the gas will not diffuse into the air and mix with it, we shall have a balloon which would float in air provided the bag and the hydrogen it contains do not weigh more than eighty pounds. As we rise from the surface of the earth, the air becomes less and less dense, or, in other words, it becomes lighter, and the balloon will keep on rising through the atmosphere until it reaches a point at which its But there are many conditions that affect the height to which the balloon will ascend. The higher we rise, the colder it is apt to become, and cold has a tendency to compress the hydrogen, collapsing the balloon and making it relatively heavier. When the sun beats upon a balloon, it heats the hydrogen, expanding it and making it relatively lighter, and if there is no room for this expansion to take place in the bag, the bag will burst. For this reason, a big safety-valve must be provided and the ordinary round balloon is open at the bottom so that the hydrogen can escape when it expands too much and the balloonist carries ballast in the form of sand which he can throw over to lighten the balloon when the gas is contracted by a sudden draft of cold air. Although a round balloon carries no engine and no propeller, it can be guided through the air to some degree. When an aËronaut wishes to go in any particular direction, he sends up his balloon by throwing out ballast or lowers it by letting out a certain amount of gas, until ZEPPELIN'S FAILURES AND SUCCESSESBut Count Zeppelin was a man of vision. He dreamed of a real ship of the air—a machine that would sail wherever the helmsman chose, regardless of wind and weather. Many years elapsed before he actually began to work out his dreams, and then he met with failure after failure. He believed in big machines and the loss of one of his airships meant the waste of a large sum of money, but he persisted, even though he spent all his fortune, and had to go heavily in debt. Every one thought him a crank until he built his third airship and proved its worth by making a trip of 270 miles. At once That was not the end of his failures. Before the war broke out, thirteen Zeppelins had been destroyed by one accident or another. Evidently the building of Zeppelin airships was not a paying undertaking, although they were used to carry passengers on short aËrial voyages. But the government made up money losses and Zeppelin went on developing his airships. Of course, he was not the only one to build airships, nor even the first to build a dirigible. The French built some large dirigibles, but they failed to see any great military advantage in ships that could sail through the air, particularly after the airplane was invented, and so it happened that when the war started the French were devoting virtually all their energies to the construction of speedy, powerful airplanes. As for the British, they did not pay much attention to airships. The idea that their isles might be attacked from the sky seemed an exceedingly remote possibility. RIGID, SEMI-RIGID, AND FLEXIBLE BALLOONSCount Zeppelin always held that the dirigible balloons must be rigid, so that they could be driven through the air readily and would hold their shape despite variations in the pressure of the hydrogen. The French, on the other hand, used a semi-rigid airship; that is, one in which a flexible balloon is attached to a rigid keel or body. The British clung to the idea of an entirely flexible balloon and they suspended their car from the gas-bag without any rigid framework to hold the gas-bag in shape. In every case, the balloons were kept taut or distended by means of air-bags or ballonets. These air-bags were placed inside the gas-bags and as the hydrogen expanded it would force the air out through valves, but the hydrogen itself would not escape. When the hydrogen contracted, the air-bags were pumped full of air so as to maintain the balloon in its fully distended condition. Additional supplies of compressed hydrogen were kept in metal tanks. In the Zeppelin balloon, however, the gas was contained in separate bags which were placed in a framework of aluminum covered over with The body of the Zeppelin is not a perfect circle in section, but is made up in the form of a polygon with sixteen sides, and the largest of the Zeppelins used during the war contained sixteen compartments, in each of which was placed a large hydrogen gas-bag. A super-Zeppelin, as the latest type is called, was about seventy-five feet in diameter and seven hundred and sixty feet long, or almost as long as three New York street blocks. In its gas-bags it carried KEEPING ENGINES CLEAR OF THE INFLAMMABLE HYDROGENAs hydrogen is a very inflammable gas, it is extremely dangerous to have an internal-combustion engine operating very near the gas-bags. In the super-Zeppelins the engines were placed in four cars suspended from the balloon. There was one of these cars forward, and one at the stern, while near the center were two cars side by side. In the rear car there were two engines, either of which could be used to drive the propeller. By means of large steering rudders and horizontal rudders, the machine could be forced to dive or rise or turn in either direction laterally. The pilot of the Zeppelin had an elaborate operating-compartment from which he could control the rudders, and he also had control of the valves in the ballonets so that by the touch of a button he could regulate the pressure of gas in any part of the dirigible. The engine cars at each side of the balloon were known as power eggs because of their general egg shape. At the center of the Zeppelin the bombs were stored, and there were electro-magnetic releasing-devices operated from the pilot's room by which the pilot could drop the bombs whenever he chose. The Zeppelin also carried machine-guns to fight off airplanes. Gasolene was stored in tanks which were placed in various parts of the machine, any one of which could feed one or all of the engines, and they were so arranged that they could be thrown overboard when the gasolene was used up, so as to lighten the load of the Zeppelin. Water ballast was used instead of sand, and alcohol THE ZEPPELIN'S TINY ANTAGONISTSThe one thing above all others that the Zeppelin commander feared was the attack of airplanes. In the early stages of the war, it was considered unsafe for airplanes to fly by night because of the difficulty of making a landing in the dark. Later this difficulty was overcome by the use of search-lights at the landing-fields. The airplane would signal its desire to land and the search-lights would point out the proper landing-field for it. So that after the first few months of the war Zeppelins were subjected to the danger of airplane attack. Of course, on a dark night it was very difficult for an airplane to locate a Zeppelin, because the huge machine could not be seen and the throb of its engines was drowned out by the engines of the airplane The danger of the Zeppelin lay in the fact that it was supported by an enormous volume of very inflammable gas and the airplane needed but to set fire to this gas to cause the destruction of the giant of the air. And so the machine-guns carried by airplanes were provided with explosive, flaming bullets. A burst of flame within the gas-bag would not set the gas on fire, because there would be no air inside to feed the fire, but surrounding the gas-bag there was always a certain leakage of hydrogen which would mix with the air in the compartment and this would produce an explosive mixture which needed but the touch of fire to set it off. The Zeppelin was provided with a ventilating-system to carry off these explosive gases, but they could never be disposed of very effectively, and, as a consequence, a number of Zeppelins were destroyed by the tiny antagonists that were sent up by the British and the French. To fight off these assailants the Germans provided their Zeppelins with guns which would fire shrapnel shell. It is difficult for a Zeppelin to use machine-guns against an airplane SUSPENDING AN OBSERVER BELOW THE ZEPPELINOne ingenious scheme that was tried was to suspend an observation car under the Zeppelin. The car was about fourteen feet long and five feet in diameter, fitted with a tail to keep it headed in the direction it was towed. It had glass windows forward and there was plenty of room in it for a man to lie at full length and make observations of things below. The car with its observer could be lowered a few thousand feet below the Zeppelin, so that the observer could watch proceedings below, while the airship remained hidden among the clouds. But despite everything that could be done, the Zeppelin eventually proved a failure as a war-vessel because it was so very costly to construct and operate and could so easily be destroyed, and the Germans began to build huge airplanes with which bombing-raids could be continued. Strange to say, however, although the Germans were ready to admit the failure of their big airship, when the war stopped the Allies were actually building machines patterned after the Zeppelin, but even larger, and expected to use them for bombing-excursions over Germany. This astonishing turn of the tables was due to the fact that America had made a contribution to aËronautics that solved the one chief drawback of the Zeppelin. A BALLOON GAS THAT WILL NOT BURNWhen we entered the war against Germany, our allies placed before us all their problems and among them was this one of the highly inflammable Every now and then the moon bobs its head into our light and we have a solar eclipse. But our satellite is not big enough to cut off all the light of the big luminary and the fiery atmosphere of the sun shows us a brilliant halo all around the black disk of the moon. Long ago, astronomers analyzed this flaming atmosphere with the spectroscope, and by the different bands of light that appeared they were able to determine what gases were present in the sun's atmosphere. But there was one band of bright yellow which they could not identify. Evidently this was produced by a gas unknown on earth, and they called it "helium" or "sun" gas. For a quarter of a century this sun gas remained a mystery; then one day, in 1895, Sir William Ramsay discovered the same band of light when studying the spectrum of the mineral cleveite. The fact that astronomers had been Because the gas had no commercial value, there was only a small amount of helium to be found in the whole world. Not a single laboratory in the United States had more than five cubic feet of it and its price ranged from $1,500 to $6,000 per cubic foot. At the lowest price it would cost $3,000,000,000 to provide gas AMERICAN CHEMISTS TO THE RESCUEJust before the war it was discovered that there is a considerable amount of helium in the natural gas of Oklahoma, Texas, and Kansas, and Sir William Ramsey suggested that our chemists might study some method of getting helium from this source. The only way of separating it out was to liquefy the gases by subjecting them to extreme cold. All gases turn to liquid if they are cooled sufficiently, and then further cold will freeze them solid. But helium can stand more cold than any other and this fact gave the clue to its recovery from natural gas. The latter was frozen and one after another the different elements condensed into liquid, until finally only helium was left. This sounds simple, but it is a difficult matter to get such low temperature as that on a large scale and do it economically. To be of any real service in aËronautics helium would have to be reduced in cost from fifteen hundred dollars to less than ten cents per cubic The reduction in the cost of helium is really one of the most important developments of this war. By removing the fire risk from airships we can safely use these craft for aËrial cruises or for quick long-distance travel over land and sea. For, even in time of peace, sailing under millions of cubic feet of hydrogen is a serious matter. Although no incendiary bullets are to be feared, there is always the danger of setting fire to the gas within the exhaust of the engines. Engines have had to be hung in cars well below the balloon proper. But with helium in the gas-bags the engines can be placed inside the balloon envelop and the propellers can operate on the center line of the car. In the case of one Zeppelin, the hydrogen was |