ON May 23rd, 1661, Samuel Pepys noted in his diary: "Elias Ashmole, the antiquary, did today assure me that frogs and many insects do often fall from the sky, already formed". And such occurrences are not unknown here in Ireland. As early as AD 1224 the Four Masters wrote of an "awful and strange shower" in Connacht; we are not told the nature of the precipitant, but assured that the shower was followed by "terrible diseases and distempers among the cattle that grazed on the lands where this shower fell."
Occurrences such as these are assumed to be the result of localised whirlwinds capable of sucking up small objects in their path. The objects may then be suspended for some considerable time in the powerful up draughts before being deposited quite some distance away, perhaps in the course of a heavy, thundery shower. And some meteorologists are of the view that they may explain the periodic appearances of the Loch Ness monster and other similar phenomena: they think that what people really see is a water devil - and in case this seems like "a rose by any other name," let me explain.
A water devil is a kind of poor relation of the waterspout - which is in turn a water based and weaker version of a tornado. All of these disturbances are vigorous "small scale local whirlwinds, which occur in what meteorologists call an unstable mass of air - an atmosphere which is anomalously warm at lower, levels. In such circumstances there is a strong tendency for brisk up draughts to form, and it sometimes happens that these ascending fountains of hot air are triggered into a strong rotating and self accelerating spiral.
The water devil is the gentlest of these phenomena. It has a lifetime of anything from one to 10 minutes, and is closely related to the more familiar dust devil which forms over land in very hot weather. Despite its relative lack of ferocity, a water devil is capable, nonetheless, of agitating the underlying water into a seething cauldron of activity, and of sucking up spray and water weed to some considerable height. I am told that they are often seen on the lakes of Co Kerry, where they are known by the local name of "rowdows" or "roudous."
Some meteorologists believe, that it is occasional water devils like these, moving slowly across the surface of a lake and producing a long narrow solid looking "neck" that lie behind the reported sightings of Nessie and other "monsters."