"Exitabat enim fluctus in simpulo," said Cicero dismissively, coining a phrase about an acquaintance he considered something of a fusspot "He was the kind of man to raise a storm within a teacup." Meteorologists, however, also have their problems with tempests and receptacles. The standard raingauge is only five inches in diameter little bigger than a teacup if you think about it and yet its contents must be assumed to have captured the whole character of a rainstorm over an area of several square miles.
When the first rain gauge was set up, who had the bright idea, or even in what country the whole rigmarole began, we do not know. We are aware that the Greeks kept systematic weather records of a kind as early as the 5th century BC, and that quantitative rainfall measurements were made in Palestine in the first century AD. But since the very earliest times the design of the raingauge has varied very little and today they are deployed in great numbers in virtually every country in the world.
Rainfall, as measured in a raingauge is measured in inches or millimetres. In either case the figure reported describes the depth to which a flat and impermeable surface would be covered by water in a given period, assuming that none of the liquid disappears by run off or evaporation. It is a highly theoretical concept obviously, in real life, such surfaces and such conditions are quite impossible to come by, but it is a useful measure which has stood the test of time.
In a typical year, by this reckoning, if our Irish precipitation were to be spread evenly over the whole country, the national average would be something like 1,150 millimetres. In other words, if the island were entirely flat and leak proof, and if it were bone dry on January 1st, and if none of the water falling on it in the 12 succeeding months were allowed to escape or to evaporate, then by the end of December the country would be inundated to a depth of 1,150 millimetres a national flood nearly four feet in depth.
Going a little further, we know that an inch of rain covering one acre of ground weighs about 100 tons. Our average yearly total, therefore, would press down on Ireland with a weight of some 4,500 tons on each of its 20 million acres a total, if you work it out, of some 100 billion tons of water, or enough to fill 450 billion 40 gallon drums. How many teacups, or indeed how many storms, that total may amount to, I will leave to you, dear gentle reader, to work out.