National Geographic : 1900 Jun
240 PREVENTION OF HAILSTORMS BY USE OF CANNON Casale Monferato. At this congress the minister of agriculture was represented by the under secretary of state, and the ministries of war and the interior also sent delegates. Five hundred participants in the congress appeared, some of them the most distinguished scientists of Italy. Mr Stiger was elected honorary president, and a committee of four eminent professors, representing Styria, Piedmont, and Venice, were appointed to report on the results of the Stiger method for pre venting damage from hail. The committee unanimously agreed that "if the shooting was commenced in time the damage from the hail was always averted." A number of instances were cited showing that in the towns where there was no shooting the destructive violence of the hail continued unabated, whereas in the districts where the shoot ing was done no hail occurred. Mr Stiger, the inventor, however, particularly warns the public against being oversanguine, as he asserts that, in spite of the many successful results obtained by his process, there is not yet the cer tainty of its effectiveness. Every one is naturally asking the question, How can the formation of hail be influenced by "weather firing "? I confess that I am not able to answer, but I must assert that because we cannot comprehend the process we have not the right to deny its existence. In explain ing the action of the cannon, two points are to be considered-the effect of the explosion and the force of the vortex ring that rises from the gun barrel. In the sultry, distressing calm that precedes violent storms it is almost a natural necessity to make a noise, and as loud a noise as possible. One feels that from the sultry calm before the storm misfortune is to come, and that by disturbing the stillness the misfortune may be turned away. Mr Stiger states that he was guided by this thought when he began his experiments in 1886. "Theob servation," he says, "that every hailstorm is preceded by an abso lute stillness of the air, accompanied by heavy oppression, suggested to me the idea of disturbing this calm which seemed essential to the formation of hail, and therefore I tried 'weather shooting,' which has been known for centuries." That vibrations can destroy the formation of hail has no founda tion in physics. As far as our knowledge reaches, for we do not yet understand the hail-forming process, the explosion could not affect the process, either through changes in the clouds, or by the prema ture freezing of droplets through concussion, or through a consider able concussion.