Until the middle of the last century, the existence all over Europe of gigantic boulders, different geologically from their surroundings and obviously transported to their present location from some distant spot, posed a problem for many of those with an interest in such matters.
To the Catastrophists, however, the solution was quite simple - it was obvious that these erratics, as they were called, had been carried to their destination by great currents of water and mud, deriving from the biblical deluge at the time of Noah.
Catastrophism, in fact, was the dominant geological philosophy in the 18th and early 19th centuries. It neatly accounted for the fossilised remains being unearthed from time to time by inquisitive geologists, and also had the convenient advantage that it did not undermine the word of God, as set forth in detail in the books of the Old Testament.
Indeed, it was commonly believed that the whole history of life on Earth was divided into several epochs, each one of which terminated in a catastrophe; at the beginning of each epoch, new life was breathed into the ravaged world - life which would survive only until the next great cataclysm came along.
In the early 1800s some scientists began to question this traditional explanation. Were flood waters, they wondered - even divinely inspired ones - capable of transporting these gigantic boulders over hundreds of miles?
Refinements to the theory were introduced to make it more plausible. Some believed, for example, that the erratics had slipped off boulder-laden icebergs, or "ice-rafts", that had drifted about in the great flood.
It was a Swiss geologist, Louis Agazziz, who promulgated the real explanation for erratics. In 1834 the 27-yearold professor of natural history at the University of Neuchatel - whose birthday, incidentally, occurs today, May 28th - championed the ideas of a more diffident colleague, Jean de Charpentier, and outlined the astounding theory that most of Europe had at one time been covered by a thick layer of ice.
Its motion, he declared, had gouged deep grooves in the underlying terrain; the ice had also swallowed up large chunks of rock in its path, and deposited them in splendid isolation many miles from their point of origin.
Agazziz visited Ireland in 1840 and identified several landscapes in Cavan, Down and Dublin that illustrated his extraordinary theory. But the idea was slow in catching on, and the acrimonious dispute on the relative plausibility of glaciers and catastrophes continued for a quarter of a century. It ended with the universal acceptance of the ice-age theory.