i6o 



NA TURE 



[June 13, 1901 



cost of the protection exceeding that of any damage 

 likely to be caused by the hail. 



The idea that the weather can be affected by the dis- 

 charge of gunpowder is not a new one. There have 

 been various traditions of rain falling after, and pre- 

 sumably in consequence of, the cannonade of a battle, 

 and I have some recollection of an account in English 

 newspapers of an American enterprise for terminating 

 a drought by a sufficiency of gunpowder. 



Weather shooting as now practised has, however, a 

 more definite purpose than merely causing rain. Its 

 object is to prevent the downpour of hail by shooting 

 when thunder or hail clouds threaten. Even this form 

 of the application of gunpowder to the management of 

 the weather is by no means new. The Mcteorologische 

 Zeilschrift of March 1900 states, on the authority of 

 Arago, that in the seventeenth century a fleet, anchored 

 off Cartagena (South ."Xmerica), dispersed a daily after- 

 noon thunderstorm by a daily bombardment : and 

 Leonardo da Vinci is said to have asserted that damage 

 by hail could be averted by mounting mortars on the 

 hills from which the storm-clouds came and shooting at 

 them. Quite early in the past century the matter was 

 taken up in the neighbourhood of Macon. The recent 

 development, which has spread very widely, is most con- 

 spicuously represented by the arrangements of Burger- 

 meister Stiger, of Windisch-Feistritz, in Styria, where 

 they were originally introduced in 1S96 in the form of a 

 vine-dressers' volunteer artillery. Batteries of ten heavy 

 mortars to take a charge of 120 grammesof powder, served 

 by six men each, were placed at twelve separate stations 

 within two square kilometres ata high level near Windisch- 

 Feistritz. As soon as a downpour of hail threatened, the 

 120 mortars were fired " incessantly " until the danger 

 was past. The second year thirty-three stations were at 

 work, and the third fifty-six. It is reported that this 

 energetic proceeding has completely protected the region 

 from hail and has mitigated the damage from lightning ; 

 and as Blargermeister .Stiger apparently introduced the 

 system as an alternative to covering the district 

 with wire of close mesh, the damage must have been 

 previously regarded as a serious matter. Other places 

 have been less successful, and the Austrian Government 

 and local authorities have taken steps to inquire into the 

 effectiveness of the shooting. But the vineyard districts 

 are not willing to wait for the report of the inquiry ; they 

 are satisfied that they only failed because they did not 

 shoot early enough or often enough, and only desire to 

 shoot more and oftener. 



It is not quite clear how the effects of the shooting 

 are manifested. In some cases it would appear that the 

 shooting dispersed the clouds altogether, in others that it 

 caused rain, sometimes heavy rain, sometimes a genial 

 and welcome rainfall instead of the malignant pelt of 

 the hail. 



Dr. Pernter, of the Austrian Meteorological Depart- 

 ment, was of the commission appointed to inquire 

 into, the matter, and in the September number of the 

 Mcteorologische Zeitschrift he gives a most interesting 

 account of some experiments in connection with the 

 inquiry. From that account it appears that there are 

 three forms of apparatus employed, differing in size. A 

 small cylindrical niortar with a large conical mouthpiece 

 is the general form of the apparatus. 



The conical portion of the smallest system (System 

 Unger) is 2 metres long, that of the longest (System 

 Suschnig) is 4 metres long ; the former takes a charge of 

 powder up to about 60 grammes, the latter up to about 

 250 grammes. Briefly, the latter is the most effective 

 implement, and a charge of 180 grammes is the best 

 suited for the purpose. 



The effect of the shot is to produce, besides noise, a 

 vortex ring of most impressive dimensions and energy. 

 It would start with a loud hum and settle down to a 



NO. 1650, VOL. 64], 



whistle. When the gunpowder charge was most suitable, it 

 would tear a thick paper screen to pieces at 100 metres 

 distance from the mortar and pull the wooden frame- 

 work of the screen apart and hurl the pieces about. Dr. 

 Pernter, indeed, becomes quite eloquent in his description 

 of the behaviour of these rings as astonishing physical 

 experiments quite apart from any practical interest they 

 may have as affecting the weather. 



The position of the ring is recognisable by its whistle 

 after it has become invisible, and its duration is estimated 

 by the duration of the whistling. In the firing the rings 

 are shot upwards, and it is assumed that the effect of the 

 shooting depends upon them. 



Dr. Pernter's experiments were directed mainly towards 

 ascertaining the velocity and the length of the path 

 of the rings, with the ultimate object of determining 

 whether they could reach the levels of the lowest stratum 

 of rain cloud. Determining the velocities from a very large 

 number of experiinents with charges of different weight, 

 he obtained in the most favourable circumstances 

 with the Suschnig apparatus an initial velocity of about 

 55 metres a second and a height of 400 metres as the 

 extreme probable limit of the best shots. Thus the 

 experiments seem to show that the rings would not reach 

 the storm-clouds at the 1 000-metre level, but as the local 

 people were convinced from their own observations that 

 the storm-clouds in the neighbourhood of St. Katherein 

 (where the experiments took place) were to be found at 

 800 metres, and as the shooting-gear was fixed at 

 elevations of some 500 metres, it seemed possible that the 

 rings might just reach the clouds. 



Such is the result of the investigation, with the addition 

 that the smaller apparatus would not carry nearly so far, 

 nor would the rings have anything like so much energy 

 as those from the larger apparatus, whence it follows 

 that if we wish to shoot the clouds effectively we 

 must use the largest-sized mortars, taking 180 grammes 

 of powder, and we should then be a little uncertain 

 whether the ring would travel far enough. 



Various theories have, of course, been suggested to 

 account for the protection from hail alleged to be secured 

 by this shooting. Supersaturated air from which the 

 rain is liberated, a labile state of atmospheric equi- 

 librium disturbed by the discharge, globules of over- 

 cooled water, still liquid below the freezing-point, which 

 would form large hail-drops if they were allowed to 

 coalesce but are solidified separately by the shock, and 

 many other suggestions have been put forward as the 

 state of things precedent to the hail shower, which is 

 disarranged by the shooting. There seems, indeed, to 

 be a disposition to see what curious conditions our 

 present knowledge of the physics of the atmosphere can 

 account for, and then wonder whether one of them might 

 be the condition of things in a thunder eloud. Theory is 

 very much at a disadvantage, because it is not at all clear 

 what has to be explained, and it is, indeed, difficult to 

 account for facts when we do not know what are the 

 facts to be accounted for. 



Dr. Hann has suggested, very properly, that the effect 

 of shooting upon a winter fog should be ascertained. 

 There appears to be some evidence that gun-firing clears 

 the air of such a fog. But whether theory is to regard 

 the noise or the smoke or the energy of the vortex ring 

 as the cause of the effect, or whether, indeed, there is 

 any effect to be explained, is not yet finally established, 

 .■^t the same time, no one is prepared to say that no 

 effect is possible or is willing to lay claim to sufficient 

 knowledge of the conditions of the atmosphere im- 

 mediately preceding a hailstorm to venture any cate- 

 gorical opinion on the various theories. The subject was 

 brought before the conference of meteorologists last year 

 at Paris by several writers, and some additional infor- 

 mation about it will doubtless appear in the report of 

 that conference when it is published : in the meantime. 



