Your own personal forecast

Press, 4 April 1989, Page 22

Your own personal forecast

Since childhood days, barometers have fascinated me. Perhaps because we did not possess one ourselves, I was impressed by these splendid instruments mounted in the homes of various friends and relatives. They added charm and dignity to their surroundings and, when tapped by the -master of the house, he was then mysteriously enabled to announce with an air of authority, the weather prospects for the day.

I am not sure why, but it seemed to be taken for granted that it was the father’s right to do this and even in these days of equal rights the custom appears to have survived to some extent.

I have discovered that most barometers purchased today are bought by women as gifts for men. In spite of the ready availability of radio, television and other sources of instant information, there is still satisfaction in do-it-yourself forecasting. Poor father must often have been proved wrong because inscriptions on the dials of barometers indicating “Very Fair,” “Fair,” “Change,” “Rain,” etc., are not really reliable guides to the weather.

It is the way the mer-

cury moves, not its height, which is a guide, and if the instrument is to be of any real value at all for this purpose, it needs to be observed frequently, which is the reason that it is equipped with two hands, one a “dummy” which can be set against the main pointer so that the extent of any change can be seen at the next reading. Barometers were originally designed to measure air pressure and much research and experimentation was carried out during the seventeenth century to this end. An Italian mathematician, Evangelista Torricelli, is credited with its invention in 1643. Further research by French scientists, among them, Blaise Pascal, Florin Perier and Rene Descartes, demonstrated the decrease of air pressure with altitude. However, it was an AngloIrishman who first used the term, “Barometer,” in 1663. He was Robert Boyle, seventh son and fourteenth child of Richard Boyle, first Earl of Cork.

The simplest form of barometer consists of a tube about one metre high which stands in such a way that the lower end is immersed. Such an instrument is cumbersome and

not easily moved. The next development was in the form of a bent or siphon tube in which the air acted on the surface of the mercury in the short tube. Other refinements followed and the barometers were housed in elaborate cases, becoming so popular that in 1708 one Richard Neve commented that “Few Gentlemen were without them.”

During the nineteenth century, the popularity continued and with the increasing wealth of the middle classes, the demand for them was widespread, involving the craftsmanship of cabinetmakers, clock-makers, in-strument-makers and opticians.

Most of the surviving mercury barometers are from this period. All are worth collecting, but as always, increasing demand tends to bring about deterioration of craftsmanship. Collectors seeking the best should watch for products of Nairn and Blunt, Troughtons, Wat-

kins and Hill, and Negretti and Zambran. In 1843, Lucien Vidie, of France, invented the aneroid barometer, which used an evacuated metallic diaphragm consisting of two corrugated, cupped discs of flexible metal welded together. This device reacted to atmospheric pressure by infinitesimal variations in thickness, which were conveyed to the pointer by means of a hairspring mounted on the shaft. Convenient and small, the aneroid revolutionised the produettion of barometers. They no longer needed to be one metre high and perpendicular, and could be produced more cheaply. Instant re-action could also be obtained by a slight tap on the glass. It was the aneroid barometer which gave rise to this now timehonoured habit. If you are collecting only mercury barometers, it is wise to remember that early aneroid instruments were often housed in cases resembling those used for the earlier pieces, but it is not difficult to distinguish one from the other. All mercury barometers will have a door at the back to allow access to the tube. Also careful examination will often reveal the word,

"Aneroid,” in very small print on an instrument resembling a mercury one. Expert opinion seems to agree that the very best antique barometers are those made in Germany in the first half of the nineteenth century. Some, bearing the mark of London retailers, contain a German movement which would seem to support this view. The most handsome cases appear to have been produced in the period from 1880 until World War I. Barometers illustrated are from Aldous Antiques in Manchester Street. They include a modern barometer incorporating a clock, thermometer and hydrometer (top left); an Edwardian banjo type; a barometer and thermometer from about 1930; and a barometer made by Hicks of London with a dual scale (sea level and natural). The small, round hand-held device is a surveyor’s barometer. These were used by two people working together, one at sea level, the other at higher altitudes. Not photographed, but in the same shop, is a handsome, brass marine barometer, gimbal-mounted.

‘Mercury barometers are worth collecting’