Meteorology sometimes runs in families. Francis Beaufort, for example, who devised the Beaufort Scale of Wind Force, was born in 1774 in Navan, Co Meath, and was a member of one such family whose meteorological connections continue into the present century.
Beaufort was brother-in-law to Richard Lovell Edgeworth. Edgeworth, who lived from 1744 to 1817, is perhaps better known as the eccentric father of Maria Edgeworth, author of Castle Rackrent and other minor classics, but he was also an enterprising scientist in his own right. He invented inter alia an interesting device for measuring humidity. The toy, for such indeed it was, would "walk" along a level surface and its rate of progress in a given time was a measure of the moisture content of the air.
Edgeworth's device consisted of a length of wood, cut crosswise to the grain, and fitted with four sharp-pointed metal "legs", inclined backwards like pikes' teeth. In humid conditions, the wood expanded slightly and the front legs slid forward across the surface while the back legs kept their grip; as the air dried out the wood shrank and the front legs dug in while the tail was dragged along. Over a period, the "creature" moved progressively forward, propelled by rises and falls in the humidity, providing, as Edgeworth put it, "a rough indication of the comparative moisture of the air".
Edgeworth, however, was singularly unlucky with his wives, and lost three in quick succession. In 1797 he took a fourth, Fanny Beaufort, sister of the future admiral. Then in 1838, to cement the bond between the tribes, Beaufort, now a widower, married Edgeworth's daughter, Honora, half-sister of the author Maria, and became Edgeworth's posthumous son-in-law.
Another of Edgeworth's daughters, Lucy Jane - who, to complicate the issue even further, was the daughter of Beaufort's sister, Fanny Beaufort Edgeworth - married Thomas Romney Robinson. Robinson, although a working clergyman, spent much of his life as director of Armagh Observatory, and designed the familiar rotating cup anemometer which has become the standard method of recording wind speed.
And finally, in the last quarter of the 19th century, Thomas Romney Robinson's daughter, Mary Susanna, married Sir George Gabriel Stokes. Stokes, who died in 1905, is remembered by physicists for Stokes's Law and by mathematicians for Stokes's Theorem. For meteorologists, he is the man who designed the instrument which uses a glass sphere for measuring the duration of bright sunshine, and which is still in daily use as the Campbell-Stokes sunshine recorder.