Courtesy of American Philosophical Society Figure 3. Uniform rate of ascent of pilot balloon up to 20,000 meters where balloon sprung a leak loons, while the temperature has been determined at the proving grounds by sending self-recording instruments aloft in specially constructed box-kites, as well as by sending self-recording instruments and meteorological observers aloft in airplanes. It has been with the aid of observations of this sort that the new range tables for the Ordnance Department of the United States Army have been constructed. The importance of this work may be understood when it is considered that these range tables will be used in connection with the firing of all guns, and errors in them would produce errors in the range of every gun fired with their aid. 3. The Development of Long Range Propaganda Balloons. - In view of the fact that above an altitude of 10,000 feet 95 per cent. of the winds both over western Europe and over the United States blow from west to east (i. e., have a westerly component), Captain Sherry in 1917 suggested the development of a large program for the extension of the use of pilot balloons for the purpose of flooding the whole of Germany and Austria with propaganda dropped from such balloons. The project was submitted to the meteorological and military agencies in France and pronounced infeasible, chiefly because the rapid diffusion of hydrogen through rubber had heretofore rendered it impossible to obtain pilot balloon flights of more than about 100 miles. Undiscouraged, however, by these reports, Mr. W. J. Lester, Dr. S. R. Williams and Sergeant Redman attacked the problem of extending the range of pilot balloon flights by developing an automatic ballast-control and by reducing the diffusion by means of a special dope. The automatic control was ingeniously simple, its essential feature being a belly band which kept the girth of the balloon constant (at a diameter of four feet) through the discharge, in the act of shrinking, of a few drops of kerosene, thus causing reascension and consequent expansion. With this device the balloon not only does not fall but rises very gradually to higher and higher levels until its ballast of kerosene or alcohol is exhausted. In the week beginning October 3, 1918, sixty such balloons, adjusted to fly between the initial and final altitudes of 15,000 and 25,000 feet respectively were sent up from Fort Omaha, Nebraska, carrying return cards and watches, which were arranged to stop and be let down on small parachutes as soon as the ballast was exhausted. Thirty-four out of sixty of these balloons were picked up and returned to Washington. Instead of flying 100 miles, one of them came down within ten miles TABLE 1 WAR DEPARTMENT, SIGNAL CORPS, U. S. ARMY, METEOROLOGICAL SERVICE. Station Ellendale, N. D. (90th Meridian Time.) |