But the problem which he had to face was that up to that time no fabric had been made which was thoroughly airtight. Happily, just when he was experimenting with hydrogen, two brothers named Roberts discovered that it was possible to apply a coating of dissolved rubber to silk fabric and thereby secure an airtight covering. This fabric was fashioned into a balloon, and on 20 Aug. 1783, the balloon, made possible by the co-operation of the genius of St. Fond and the Roberts brothers, was filled with hydrogen and liberated. It rose to a very great height, but because of too strong inflation it ruptured and the envelope fell to the ground.
The tests thus commenced were continued by De Rozier, and Count Zambeserri, until in January 1785, Blanchard, a professional balloon ist, accompanied by Dr. Jeffries, an American, drifted across the English Channel from Dover to Calais. To-day a marble column marks the spot on the coast at Calais where this historic landing was made.
The next important advance in practical ballooning was made by the substitution of coal gas for hydrogen. This was England's contri bution to an art which previously had not greatly flourished west of the channel. It was a contribution following the natural growth of science, for in 1814 coal gas began generally to be used for lighting in London and several years later for inflating balloons. This valuable advance was made by the famous aeronaut Charles Green. It gave a powerful stimulus to aeronautics by rendering inflation cheap and convenient. The first aerostat con structed on anything like our present propor tions was the great balloon of Nassau which, on its initial journey, was navigated from Lon don to Weilburg, a distance of nearly 500 miles. This was in 1836. In 1863 a still more elaborate and colossal airship was the Giant. It was made of .a double layer of white silk, had a volume of 215,000 cubic feet and a buoy ancy of 41/2 tons. The Giant was in turn eclipsed in size by the great balloon of Henri Giffard. This measured 450,000 cubic feet and even to-day ranks as the largest captive bal loon ever constructed. It was a familiar ob ject at the Paris Exposition in 1878.
On 31 July 1901 Professor Bergson of Ger many, accompanied by Dr. Suring, ascended in the balloon Preussen to an altitude of 10, 800 metres (6.7 miles), which at present
stitutes the world's altitude record. No serious attempt has been made to surpass this altitude record, for though it is easily possible to carry human beings to a greater height than seven miles, the results seem hardly to justify the cost. To ascend very much higher would re quire an enormous and costly balloon and to ensure the comfort of the passengers might re quire an airtight car, or armor, supplied con tinuously with fresh air or oxygen.
In recent years some of the most notable balloon flights include that of M. Goddard, who sailed from Leipzig to Wilna, a distance of 1,032 miles in 241/2 hours. This was in 1897. In 1900 M. Balsan voyaged from Vincennes, France, to Rodom, Russia, a distance of 843 miles in 27 hours and 25 minutes, and De la Vaulx, starting from the same point, landed at Korosticheff, Russia, having traversed 1,193 miles in 35g hours. Until 1912 this remained the longest balloon flight on record. A close second to this record was made by Alan R. Hawley in his spherical balloon America, aided by Augustus Post, in the Gordon Bennett In ternational Balloon Race in 1910. Sailing from Saint Louis they drifted 1,172 miles from their starting point and landed in a great for, est at Peribonka River, North Lake Chilogoma, Quebec, Canada. In 1912 MM. Dubonnet and Dupont started from La Motte-I4reuil, France, in the Condor III and landed at Sokolowska, Russia, having traversed a distance of 1,211 miles. This record was supplanted in. the same year by that of MM. Bienaime and Rumpel mayer in the Picardie. They started from Stuttgart, Germany, and in 48 hours landed near Moscow, Russia, after a trip of 1,3610 Rumpelmayer made a new record on 24 March 1913 by a trip of 1,492 miles from Paris to a point near Kharkoff, Russia.
The recent advances in aerostation, though not radically changing the balloon itself, con tribute much to its use and convenience. Im provements have occurred in the means of inflation and deflation, in devices for making topographical and meteorological observations, as also for transmitting and receiving signals. Hydrogen shipped in steel tubes is now avail able for easy and rapid inflation, the process of obtaining it on a large scale making it prac tically as cheap as illuminating gas.