National Geographic : 1900 Jun
PREVENTION OF HAILSTORMS BY USE OF CANNON 241 We must therefore turn to the second hypothesis, that the effect of the vortex ring from the cannon prevents the formation of hail stones. Mr Stiger has from the beginning ascribed the successful results from his machine to the effects of the vortex rings. In an official report of an expert from the Imperial Institute, who was sent to investigate the experiments made by Mr Stiger in 1897, the following statement is made: " It was shown that by the discharge of a shot a vortex ring similar to the common smoke ring is produced and can be seen in reflected sunlight. The ring rises rapidly with a distinct whistling, which is audible at a great distance. Observations showed that this whistling could be heard for 13 seconds, and in calms for more than 20 seconds." A swallow which was once struck by one of these vortex rings fell dead, such was its tremendous force. Mr Stiger estimates the effect iveness of the shots and the shooting apparatus from the duration of the whistling of the vortex ring. Step by step the size of the mortar, the depth and breadth of the bore, the form and height of the barrel, the weight of the powder, have been carefully determined by exper iment, until a most effective combination has been attained. In some experiments, at which I was present, I saw the vortex ring shoot up ward against the clouds like a shot from a gun barrel, and distinctly heard the whistling for 20 to 28 seconds. The astounding force of the vortex ring was best demonstrated by the horizontal shot. A series of peculiar targets were placed at distances of 40, 60, 80, and 100 meters. When the vortex ring struck the targets it threw down poles which were braced with heavy linen cloth, burst through paper targets in which the paper had a resistance of 12 kilograms, tore loose clamps, and broke one clamp which was 3 centimeters long and 1* centime ters broad. A large bulldog which was in the way of the vortex ring was tumbled over twice and lost all desire for further observation. In this mechanical power of the vortex ring we have found the force which may possibly influence the process of hail formation. Un fortunately, as I have mentioned before, we know too little of the process of hail formation to be able to explain more clearly the action of the vortex ring, which certainly exerts a considerable force to a height of from 1,500 to 2,000 meters.