Zeus, the chief god of the ancient Greek world, was responsible for weather matters. He was usually depicted seated on a throne clutching missiles called "thunderbolts", which, when displeased, he would hurl at all and sundry, the onslaught being accompanied by a thunderstorm. The bolt itself was portrayed as an object rather like a dumb-bell, a short bar equipped with cone-shaped nodules at either end.
The belief in thunderbolts persisted long after Greek and Roman times. There was a common conviction that the destructive power of lightning was due, not to the lightning itself, but to a missile or mass of heated matter that was discharged from thunderclouds during a storm.
Naturally enough, people tried to find traces of these destructive implements in the aftermath of thunderstorms, and sometimes believed they had succeeded when they came across objects known as fulgurites. .
When lightning strikes dry rock or sand, the heat of the discharge sometimes fuses a wedge of the material into a solid lump of glass. More often, particularly in the case of sand, it leaves a hole surrounded by a tube of glass.
In either case, the resulting glassy objects are fulgurites, and with their sudden appearance after a violent thunderstorm, one can see how our ancestors might have thought they came from heaven. In loose sand, fulgurites can be many feet in length, and are typically half an inch or thereabouts in circumference. Compression of the glass by steam from the intense heat of the ground outside often gives to the fulgurite a somewhat "ribbed" exterior.
The longest fulgurite ever discovered is reputedly that unearthed in northern Florida in 1996 by Prof Martin Uman of the University of Florida, who at the time was carrying out research on lightning.
With painstaking care, he and his team uncovered a fulgurite that turned out to have forked into three branches, one over 14 feet long, another 16 feet, and a third about eight feet in length.
To ensure that the specimen was retrieved undamaged from the sandy soil, they enlisted the help of a palaeontologist who was able to bring his expertise in dealing with fragile fossils to bear upon the challenge.
Fulgurites - named from the Latin fulgur, , meaning lightning - are common in the Alps and in the Pyrenees, in parts of North America and anywhere in the desert regions of the low latitudes. But from his wide experience Prof Umam is of the view that fulgurites are not as rare as one might think. "The world is full of them," he says. "All you have to do to find one is go to any beach and dig."