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operated from the car. The total weight of the propelling machinery, the car and the appurtenances, exclusive of 850 pounds of ballast, was 1200 pounds, while the balloon itself weighed 600 pounds. With the propeller making 180 revolutions per minute this balloon was able to maintain its position against a wind blowing 6.8 miles per hour, and when traveling with the wind to deviate to one side or the other with This balloon was followed by one of the French Government, whose construction was suggested by Tissandier's experiments, it being designed by MM. Renard and Krebs on similar lines to, but somewhat longer in comparison with its diameter than, Tissandier's. Seven ascents were made with this balloon during 1884-85, with the following practical results: In five of the ascents the voyagers were able to return to their starting point, and in one instance a velocity of 13 miles per hour was attained independently of the wind.

A notable airship, both for its size and design, was that in which Count Zeppelin made his voyages in 1900. It consisted of a row of seventeen balloons, confined like lozenges in a pack age, in a cylindrical shell 420 feet long and 39 feet in diameter, with pointed ends. These balloons serve to lift the structure in the air, where it is driven forward or backward by means of large screw propellers operated by benzine motors. A pair of rudders, one forward and one aft, serve to steer the 'airship.' The crew and passengers occupy two aluminum cars suspended forward and aft, below the body of the balloon shell. From these cars, which are connected by a speaking tube, all the machinery of the airship' is operated. The 'airship' is made to run on a horizontal or inclined plane by means of a weight, which can be moved back and forth, on a cable underneath the balloon shell. When the weight is far aft, the bow of the ship points upward and the movement is upward; and when the weight is far forward, the movement is downward, and when the weight is exactly in the centre of the ship, the travel is horizontal. The Daimler benzine engines, one in each car, were of 16 horse-power capacity each, and weighed 715 pounds each. The screw propellers, two for each engine, had four blades and were 34 feet in diameter. At the first trial of the Zeppelin airship on July 2, 1900, with five persons in the cars, it rose 1300 feet above Lake Constance and traveled 34 miles in 17 minutes in the direction desired. An accident to the sliding weight and to one of the rudders caused a descent to be made, which was accomplished with perfect ease. At a succeeding trial on October 17, the airship attained a height of nearly 2000 feet, and there remained poised for 45 minutes. It then made a series of tacks, and described a circle of about 6 miles circumference. The wind exceeded a velocity of about 7 miles per hour, and the airship made headway against this wind for a considerable distance. After remaining in the air for about one hour, the ship descended to the lake with great ease, and was towed to its shed. A third test was also made on October 21. In steering, stability, and equilibrium the tests were pronounced very successful. In 1905 Count Zeppelin made extensive trials of a new airship, in which were incorporated most of the features of the original construction, in addition to many improvements, largely made possible

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by the decreased weight and increased efficiency of internal combustion motors. Thus the two engines of the 1905 airship were able to supply 170 horse-power at an increase in weight of only 11 pounds, the entire machinery weighing but 880 pounds. Furthermore, the length of the new airship was decreased to 410 feet, and the number of gas compartments was made 16 instead of 17. The cubical contents of the balloon were diminished to 367,120 feet, while the weight to be lifted was smaller by 2200 pounds, amounting to about 19,800 pounds. The propellers on the other hand were of increased size. There were numerous innovations, such as liquid ballast and a complete system of vanes for vertical and horizontal steering. The large size of this balloon makes possible sustained flights, and the carrying of sufficient fuel for long trips, such as 15 to 20 hours.

In 1901, M. Alberto Santos-Dumont, a Brazilian gentleman resident in Paris, excited widespread interest through his experiments with a dirigible balloon. This aëronaut built his first balloon in 1898. It was in the form of a cylinder, terminated at each end by a cone, and was 82 feet long and nearly 6 feet in diameter, with a capacity of 6400 cubic feet. A basket suspended from the balloon carried a 11⁄2 horse-power gasoline motor, which operated a screw propeller. To provide the necessary fore and aft trim for ascent and descent when under way, the inventor made use of bags of ballast which could be attached or removed at will from ropes suspended from the forward and after part of the balloon and accessible from the basket or car. With this balloon M. SantosDumont made an ascent in the autumn of 1898 which nearly resulted fatally to himself; the failure of an air-pump to work resulted in a partial collapse of the balloon, which fell 1300 feet to the ground. Aside from the air-pump accident, the success of this trip was unusually encouraging; the balloon proved perfectly dirigible in the light winds prevailing at the time of the trip. A second balloon, built exactly like the first, but larger, was never used by M. SantosDumont, owing to the fact that in some experi ments made with his first balloon when captive the conclusion had been forced upon him that the model was incorrect. A third balloon, shorter and very much thicker, was completed in the summer of 1899. This balloon was 66 feet long, 11% feet greatest diameter, and 17,600 cubic feet capacity, and into the construction was introduced the novelty of what the inventor termed a keel. This keel was nothing more or less than a bamboo pole, 30 feet long, fixed lengthwise to suspender cords just beneath the balloon, which supported the basket and other apparatus. M. Santos-Dumont was able to circle around the Eiffel Tower in this balloon but found that it was too clumsy and the motor too weak, and he built a fourth, 95 feet long and 9 feet in diameter, elliptical in shape, with a capacity of 14,800 cubic feet. In this balloon the keel was a long framework of bamboo and wire, which carried directly-there being no suspended cara 7 horse-power motor with its propeller and other mechanism. The operator managed his machine seated on a bicycle saddle attached to the keel. With this balloon M. Santos-Dumont made numerous short trips during the Paris Exposition of 1900. Balloon No. 5 was made by cutting balloon No. 4 in half and inserting

a cylindrical piece sufficient to increase its length to 109 feet. A 16 horse-power motor was adopted. The keel was a 60 foot framework of pine and piano wire, and into it, 20 feet from the stern, was fixed the motor, while the operator occupied a basket 23 feet from the front end or stem. On August 18, 1901, M. Santos-Dumont navigated this balloon from St. Cloud to and around the Eiffel Tower, and was approaching the starting point when the balloon collapsed, and the whole structure, with its operator, was precipitated upon the roof of the Trocadero Hotel, where it hung, the keel spanning the space between the two roofs. The sixth balloon of M. Santos-Dumont was like the previous one, except that it was longer, thicker, and more nearly ellipsoidal in shape. On October 19, 1901, this balloon succeeded in making a trip from St. Cloud to and around the Eiffel Tower, and then back to the starting point, in 30 minutes, 404 seconds. The trip was undertaken as the result of a prize of 100,000 francs offered to the inventor should he succeed in making the journey in 30 minutes.

In rapid succession the Brazilian aëronaut has constructed balloons, each embodying some new feature, and in the main marking an advance over its predecessors. In some instances, notably in his No. 9, there was a return to the egg-shaped balloon of Krebs and Renard of 1885, with the larger end first, to give greater resistance to the air. In some cases speed was aimed at, in others, carrying capacity, while the control in each instance was made more complete. In 1905 the Santos-Dumont XIV was finished, a balloon designed for speed. It was 41 metres (134.5 feet) in length and was inflated with pure hydrogen. Its motor consisted of a 14 horse-power Pengot motor, weighing 27 kilograms (59.5 lbs.) and connected with a propeller placed well forward near the motor, so that the airship is drawn rather than propelled. This dirigible balloon was tested at Trowville over the sea and was found to be readily guided and controlled.

Sharing the honors with the airships of Santos-Dumont are those of M. Le Baudy which, all things considered, are thought by many authorities to be the most satisfactory and successful airships where a gas inflated balloon is employed. The 1903 airship consisted of a long and finely pointed balloon containing eighty thousand cubic feet of gas, and constructed with its lower surface flat, around which was a frame of steel tubing, from which the car was suspended. The balloon for this airship was made of two thicknesses of cotton cloth, with india rubber between, and while reasonably light, was quite impervious to the gas. There was also a keel which was made of steel tubing and covered with canvas. Extensive use was made of steel tubes and wire, and for this purpose the new nickel steel alloy, containing 12% of nickel, was em ployed. Both in the framework and in the machinery there was a solidity and rigidity of construction, and, throughout, all details were developed with a careful consideration of the best engineering principles and practice. The car was a boat-shaped frame of steel, and contained a Mercedes engine of 40 horse-power, driving steel propellers which rotated at a rate of one thousand revolutions a minute. The weight of this airship, including its passengers, was 5700 pounds. In 1903 it traveled on one

trip 61 miles, and was in the air 24 hours. The best speed recorded was 25 miles an hour, and were it not for the untimely destruction of the airship while resting on the ground in a fierce gale, much more could doubtless have been accomplished. In 1904 a new Le Baudy airship was built, embodying essentially the features of the former, and at the same time taking advantage of the experience gained. In this a motor was used whose weight was only about 7 kilograms (16% lbs.) per horse-power, and the consumption of fuel was but 315 grams per horse-power.

An important result of M. Le Baudy's experiments was the demonstration of the advantage of filling the balloon with pure hydrogen gas, as the ascensional force thus produced was about 60% greater than with ordinary illuminating gas. Consequently the gas generated by the action of sulphuric acid on iron was purified by washing and by chemical treatment in order to eliminate the various impurities, including those that tended to increase the specific gravity of the gas. So great was the success of the cotton fabric with alternate coats of india rubber employed in the earlier balloon that it was adopted for the later airships, but it was recognized that silk could be used on account of its greater strength were it necessary to construct a larger balloon. The cloth is colored yellow with the object of protecting the rubber from the actinic effects of the sunlight. The Le Baudy balloon of 1904 was cigar-shaped, with its rear end rounded. It was 57.75 metres (189.5 feet) in length; its maximum diameter was 9.80 metres (32.5 feet), and it had a volume of 2666 cubic metres, which afforded a sustaining capacity for more than three thousand kilograms, or over three tons. This enabled the balloon to lift the structure, machinery, the crew of five men, fuel for seven hours, and 300 to 350 kilograms of ballast. The motor for this airship was a 40 horse-power Mercedes gasolene motor with four cycle cylinders, designed to operate at a normal speed of one thousand revolutions per minute, and susceptible of regulation from 250 to 1200 revolutions per minute. The crank-shaft of the motor was transverse to the axis of the car, and by bevel gearing its motion was conveyed to the propeller shafts running at the same speed. The blades of the propeller had a diameter of 2.44 metres. In the experiments with this airship it was demonstrated conclusively that it could be controlled in windy weather, and could maintain its equilibrium satisfactorily. In 1905 a new Le Baudy airship was constructed, which had about the same length but greater transverse dimensions and capacity of volume of the envelope than that of the previous year, besides having a more powerful motor. This balloon was extensively tested by the French military authorities and furnished a most excellent account of itself. It was desired to try the availability of the airship for scouting and photographic surveying, and in the military ascents made at Toul it was found possible to rise above the fortresses, and to detect all of their features to the smallest detail, while at the same time the balloon could be manoeuvred at such a height as to avoid the enemy's fire. This balloon was turned over to the French army, and in 1906 the MM. Le Baudy were commissioned to construct a new airship.

Among the French dirigible balloons mention

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should be made of the airship constructed for the Wellman Chicago Record-Herald Aretic Expedition. This airship was to be used in a dash for the North Pole from a base in Spitzbergen and was designed to make a speed of about 15 miles an hour on a ten days' trip. It was 164.04 feet in length, with a greatest diameter of 52.49 feet, surface area 21,098 square feet, capacity 224.244 cubic feet. Its lifting power was estimated at 16,000 pounds, and the weight consisted of the balloon, machinery, and steel car, amounting to 6600 pounds, and the crew, instruments, supplies, etc., aggregating 9400 pounds. The contemplated duration of inflation was from 15 to 20 days, and the two motors, of 50 and 25 horse-power respectively, were able to give a speed of from 12 to 15 miles per hour. The suspended steel car was 52.5 feet in length, and contained an enclosed engineroom and cabin, while below there was a steel boat, which not only served as on a working deck for the manipulation of the guide rope, but could be used as a sledge in case of accident to the airship, necessitating a return by foot over the ice or open water to the headquarters.

In the United States many flights have been made by airships of different patterns more or less successfully. In New York, in August, 1905, several trips were made in a dirigible balloon by Roy S. Knabenshue, and again, in the following year, when the assistant of this aëronaut, Lincoln Beechey, twice went around the Washington Monument and the dome of the Capitol, showing how well an airship could be controlled in a calm or in light airs. Another ascent of similar nature was made on July 31, 1905, at Brighton Beach, New York, by Leo Stevens, who was able to navigate at will an airship known as the " California Arrow" and to return to the starting place. In 1905 and 1906 considerable interest was manifested in ballooning in the United States and the Aëro Club of America was formed, which, in January, 1906, held an exhibition at the Sixth Annual Automobile Show in New York. A large number of balloons have been made and used chiefly for sport, though but little of scientific importance or in the way of the practical advance of the art as yet has been accomplished.

High ascents in balloons have been made by a number of aëronauts. On September 5, 1862, two English aëronauts, Messrs. Coxwell and Glaisher, starting from Wolverhampton, England, ascended 37,000 feet, or fully seven miles. At a height of 5%1⁄2 miles one of the aëronauts became insensible and the other very nearly so; at the height of 4 miles railway trains could be heard, but at a height of 6 miles there was perfect silence. On April 15, 1875, M. Tissandier, the inventor of the dirigible balloon previously described, and two others rose from Paris, France, a height of 5% miles. M. Tissandier alone survived the trip, his companions dying in mid-air, and he himself being rendered unconscious. These are the two highest balloon ascents recorded in which living beings were passengers.

Scientific research by means of balloons has been undertaken in a number of instances, the most notable attempt, perhaps, in recent years being that of the Arctic explorer Andrée to reach the North Pole in the summer of 1897. As is well known, the explorer and his companions perished without accomplishing anything, but in 1906 preparations were being made for a trip to

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The

the Pole in the Wellman airship described below. The most fruitful scientific results so far obtained by ballooning have come from the study of the magnetism, humidity, temperature, and chemical composition of the air at high altitudes. first ascension of any value for these purposes was that of Gay Lussac, in 1804, from Paris. The balloon rose to 23,000 feet, and the fall in temperature was 67° F., or 1° in 340 feet. Specimens of air collected at the highest point showed precisely the same composition as at the earth. The magnetic force did not experience any sensible variation at the different heights. The next ascent of importance was that of Barral and Bixto in July, 1850. In this ascent, at 19,700 feet, the aeronauts observed a temperature in a cloud of 15° F., and at 23,000 feet above the cloud a temperature of 38° F. The ascent of James Glaisher in 1862 has already been noted for its extreme height, and there have been several other ascents of less height from which fruitful scientific results have been obtained. On March 21, 1893, a balloon 19.7 feet in diameter, carrying a self-registering barometer and thermometer, was sent up from Paris. The records made by these instruments were examined when the balloon descended, and appeared to show that the balloon rose to a height of 45,920 feet, when the ink froze at a temperature of -32° C., and the record was discontinued until at a height of 52,490 feet the ink was thawed by solar radiation and the record was resumed. The accuracy of these figures has been seriously questioned, but if they are accurate the balloon reached a height of nearly 10 miles. The importance of making meteorological observations at high altitudes has led recently to the extensive use of unmanned balloons, ballons sonde, which carry recording apparatus to considerable heights, and thus enable a study to be made of atmospheric conditions. These balloons are made of thin rubber and are filled with hydrogen gas, which enables them to reach considerable altitudes, at which the pressure of the gas suffices to burst the envelope of the balloon, while the meteorograph, which is attached to a parachute or second balloon, falls to the ground without injury. It is sufficiently conspicuous to attract attention and it is picked up and forwarded to the station or bureau, from which the balloon was dispatched. While this has been a favorite method of research in Europe for several years, it was not tried in the United States until the fall of 1904, in connection with the St. Louis Exposition, and some of these instruments were carried up to a height of 9 or 10 miles, and recorded temperatures as low as-68° F. These observations were continued in 1905 with considerable success, while in the same year the beginning of a similar set of experiments was made in England. Indeed the importance of this method of observing was recognized at an international conference held in 1904 and arrangements were made for simultaneous international ascents.

The first important test of ballons sonde at sea' was made in the spring of 1905, by the Prince of Monaco. These balloons, in addition to the essential features, also included some novel characteristics. In some cases two balloons were connected, the lower being charged at a somewhat greater pressure than the upper, so that when it broke, the upper balloon would a parachute, and carry the recording

serve as