PREVENTIOX OF HAILSTORMS BY USE OF CANNON 241 



'\Ve must therefore turn to the second hypothesis, tliat the effect 

 of tlie vortex ring from the cannon prevents the formation of hail- 

 stones. Mr Stiger has from the l)eginning 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 h}^ 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 rapidl}' 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 Avas 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 w'as 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 li centime- 

 ters broad. A large bulldog which was in the wa}^ of the vortex ring 

 was tumljled over twice and lost all desire for further oltservation. 



In this mechanical power of the vortex ring we have found the force 

 which may possil)ly influence the ])rocess of hail formation. Vn- 

 fortunateh\ as I have mentioned l^efore, we know too little of the 

 process of hail formation to be able to exi)lain more clearly the action 

 of the vortex ring, which certainly e.xerts a considerable force to a 

 height of from 1,500 to 2,000 meters. 



