Page:Popular Science Monthly Volume 64.djvu/390

386 Giffard obtained only 6.71 miles per hour, although his balloon was 144 feet long and 39 feet in diameter, or about the size of a tramp steamer.

Dupuy de Lome in 1872 went up with a balloon 118 feet long and 49 feet in diameter, but, having a wholesome dread of the contiguity of fire and inflammable gas, he employed man power (weighing about 2,000 pounds to the horse power) to drive his screws, and he obtained less speed than Giffard. The accidents to Wölfert and to DeBradsky have since shown the soundness of his fears.

Next came Tissandier in 1884, who employed an electric motor of 1 1/2 horse power, weighing some 616 pounds, with which he attained 7.82 miles per hour.

Meanwhile the French war department took up the problem. It availed itself of the labors of the previous experimenters and made careful and costly investigations of the best modes of construction, of the best shapes to cleave the air and of the weight and efficiency of motors. This culminated in 1885 when Messrs. Renard and Krebs, of the Aeronautical Section, brought out the war balloon 'La France' which attained about 14 miles an hour (or half the speed of a trotting horse) and returned to its shed five times out of the seven occasions on which it was publicly taken out.

This air ship was 165 feet long, 27 1/2 feet in diameter and was provided with an electric motor of 9 horse power, weighing with its apurtenances some 1,174 pounds. The longitudinal section was parabolic, somewhat like a cigar rolled to a sharp point at both ends, the largest cross-section being one fourth of the distance from the front, and it was driven, blunt end foremost, by a screw attached at the front of the car. No better shape and arrangement have yet been devised and subsequent experimenters who have wandered away therefrom have achieved inferior results, so far as the coefficient of resistance is concerned.

In 1893 the French War Department built the 'General Meusnier,' named after an aeronautical officer of extraordinary merit of the first French Republic. This war balloon is said to be 230 feet long, 30 feet in diameter, 120,000 cubic feet in capacity and to have been originally provided with a gasoline motor of 45 horse power. It is said by all the writers on the subject that it was never taken out. Possibly the French were waiting for a war which fortunately never came ; but, be this as it may, it is probable that with the reduction which has since taken place in gasoline motors this balloon could carry an engine of some 70 horse power, and attain a speed of about 30 miles an hour, which is greater than that of transatlantic steamers.

Some unsuccessful experiments were carried on in Germany in 1897. First by Dr. Wölfert, whose balloon was set on fire by his gasoline motor and exploded in the air, killing both himself and his