Gallery opened 10 Apr 2020
Updated 27 Apr 2020
Charleville hail cannon 1902 added
A hail cannon is not a weapon that shoots small balls of ice at the enemy. A hail cannon is intended to prevent hail by disrupting its formation in the atmosphere with acoustic shock waves. If you live in a country like Britain, where hail is relatively rare, and hardly ever bigger than peas, you may be wondering why anyone would bother. But... in other countries hailstones can be much larger and very destructive of crops. I sheltered from a hailstorm (combined with torrential rain) in Florence last year, and the hailstones were about 2 cm across. There was no obvious damage to cars but it certainly wasn't something you'd want to be caught out in. Hailstones can be as large as 6 inches across; at even half that size they can cause fatal injuries.
I will say at once that there is no evidence that hail cannon have any effect at all. Thunder creates much stronger acoustic shock waves than any earth-based cannon could, but thunderstorms with hail are not at all uncommon.
Left: The 3rd International Congress on Hail Shooting at Lyons: 1901
Historically, attempts to acoustically suppress hail began with the ringing of church bells, (in France) and moved on to rockets and cannon fired with gunpowder.
Modern developments began in 1895 when Austrian wine-grower Albert Stiger, made experiments with conical cannon.
There is a Wikipedia page for hail cannon.
Left: Hail cannon on wheels, with variable elevation
A hail cannon in the old castle at Banská Štiavnica in central Slovakia.
The box at the front of the carriage may have been intended to carry gunpowder charges.
Left: Six hail cannon in Charleville, Australia: 1902
One of the best-known attempts to use hail cannon happened in 1901 western Queensland,which was in the grip of a severe drought. Clement Lindley Wragge was official Queensland's meteorological observer, and arranged for six guns to be built in Brisbane and taken to Charleville in an attempt not to stop hail, but to break the drought.
The six hail cannon appear to have been given names; they are labelled Leahy, Susching, (?) Harvey, Philip, Stiger, and Wragge. Stiger refers to the inventor Albert Stiger, while Wragge was the meteorologist who organised the attempt. The six items in the foreground are persumably the breech assemblies.
On 26 September 1902, the breech of each was loaded with gunpowder which was detonated. No significant rain fell and the experiment was considered a failure, not least because two of the six guns reportedly exploded. (presumably this means the breech assembly failed) Blame for the failure was directed at the Charleville townsfolk, since Wragge was not on hand to oversee the experiment.
Two of the vortex guns are on display in a Charleville park.
Left: A modern hail cannon in Germany
Modern hail cannon create shock waves by exploding a mixture of acetylene and air at the apex of the horn. This one in Germany appears to be intended to protect apple or pear trees.
Despite the lack of any kind of scientific proof that they work, hail cannon are manufactured today, for example by Eggers.