BALLOON 



559 



BALLOON 



the features of a balloon of to-day. It was 

 made of varnished silk, and was filled with 

 hydrogen, which it had taken Professor Charles 

 four days to produce by the slow methods then 

 employed. Scores of thousands of people gath- 



MONTGOLFIER BALLOON 

 It operated on the same principle as the pres- 

 ent-day paper balloons, so popular with boys and 

 girls on festive occasions. 



ered to watch it as it rose over Paris, and for 

 almost an hour it remained in view, about 

 3,000 feet above the earth; but then it began 

 to drift, and later came to earth fifteen miles 

 away in a field, where it was torn to pieces by 

 the terrified peasants. The next step was the 

 sending up, in a car below the gas bag, of live 

 passengers a fowl, a duck and a sheep; and in 

 November, 1783, two men ascended in a hot- 

 air balloon to a height of 500 feet, and trav- 

 eled for five miles before descending. As 

 always when inventions are in progress, there 

 were not lacking men who, through scientific 

 interest or sheer love of adventure, were willing 

 to risk their lives in perilous balloon ascen- 

 sions, and in 1785 two men crossed the English 

 Channel from Dover to Calais. 



Modern Balloons. Improvements con 

 to be made in details, though not in principle, 

 until the balloon of to-day was evolved. This 

 consists of a bag of soft cloth, silk, woolen or 

 cotton, coated with rubber varnish and covered 

 with a network of cords, to which tlu wicker 



car for passengers is attached. In the top is a 

 valve for the escape of gas, operated by a cord 

 which reaches into the car, and the bottom of 

 the bag is left open. The gas most used is 

 coal gas, which is far cheaper than hydrogen 

 but not so entirely satisfactory because of its 

 greater heaviness. A balloon which is to carry 

 any considerable weight must be large, and 

 some with a diameter of 118 feet have been 

 constructed. 



Besides the human freight in the dangling car, 

 the aeronaut has his instruments, thermom- 

 eters and barometers for the reading of at- 

 mospheric conditions, and a quantity of ballast, 

 usually in the form of sand-bags, which may 

 be thrown out when he wishes to rise to a 

 greater height. By means of these and the 

 valve he can control his ascent and descent, but 

 that is all the guidance he can give; as to 

 horizontal directions, the balloon must move 

 "at the wind's will." Dirigible balloons or 

 "guidable" balloons, have been invented and 

 have proved most useful, but on account of 

 the machinery necessary for their control they 

 are classed rather as airships. See FLYING 

 MACHINES, subhead Dirigible Balloons. 



Uses of Balloons. The uses of these bal- 

 loons which cannot be directed are, of course, 

 limited, but they have been of value in the secur- 

 ing of scientific information as to air conditions. 

 Since men cannot breathe if more than a cer- 

 tain distance above the earth, unlimited up- 

 ward flights are impossible for manned balloons, 

 but little ones of india-rubber have been sent 

 up frequently to great heights, and the record- 

 ing apparatus attached to them gives valuable 

 information. The balloons themselves do not 

 return to the earth, for the inner pressure 

 explodes them in the thin upper atmosphere, 

 but a parachute brings the instruments down 

 in safety. In 1912 one of these sounding bal- 

 loons, as they are called, which was sent up 

 from Pavia, Italy, reached a height of 123,505 

 feet (nearly twenty-five miles) and brought 

 back the information that at that great height 

 the temperature was 60, and the pressure of 

 the air only %oo of what it is at the earth's 

 surface. 



In warfare, balloons have been used in 

 various ways. The besieged people of Paris, 

 lurmn the Franco-German War, in 1870-1871, 

 conducted most of their communication with 

 tin outside world by means of them, and since 

 that date every large country has had in its 

 military service a balloon corps. It is not the 

 freely moving balloon which is of use in mili- 



