Friday, 27 July 2007

Climate under pressure

Hurricane Charlie batters Florida, Hong Kong reports its heaviest rainfall ever, ruinous hailstorms rattle China and we here in the North West had our share too. There's so much weather about -- I've never seen so much rain fall in one place for such a sustained period -- I really could have done with that barometer.

Sadly, however, it wasn't to be. It was a good looking thing and I was keen to own it. An aneroid barometer dating for the 1920s, it caught my eye at a local collectors' fair with a price tag of £75.

The circular dial was framed in oak, the wood carved to represent rope, and although it was plain and businesslike, it was hopefully reliable. After the traditional round of bartering, it was mine for £60.

At the time, the sun was shining, so it was no surprise to see the thing reading Fine. By the time I got it home, the heavens had opened but the barometer's inertia was easily excused: it needed to settle in, bed down, get used to its surroundings. Then, no doubt, it would prove to be an indicator of what Mother Nature intended for us.

Two weeks later, and with rain and gales lashing the house, I'd had enough. The wretched barometer was stuck stoically on Fine and its credibility was zero.

I phoned the dealer who sold it to us, expecting the worst but I was pleasantly surprised and my faith in human nature was shored up. If the barometer didn't work, I should take it back. He’d give me a full refund, which was accepted gratefully (though I did say that if he could fix it, I'd have it back).

Imagine my surprise -- nay shock -- then, when the Business Manager (Mrs P) suddenly announced: "I know how to tell whether a barometer is working or not."

I pointed out, somewhat indignantly, that it was a bit late now, but the remark fell on deaf ears and she was in full flight.

"Yes," she said. "You have to take a plastic bag with you when you go to an auction or collectors’ fair. When you find a barometer you want to test, you put it inside the plastic bag, gather the top of the bag together in your hand and blow it up. Then, you carefully squeeze the sides of the bag, which causes the air pressure inside it to increase.

"Because an aneroid barometer works on air pressure, squeezing the bag makes the barometer's needle move. If it moves, it's fine, if it doesn't, it's broken."
I didn't know whether to laugh or cry! And where did she pick up this little gem of knowledge? Flog It!, she announced proudly, proving beyond doubt how she spends her afternoons when she's not at work!

So, afternoon television programmes about collecting antiques do have their uses. I, meanwhile, resolved to learn more about barometers.

They started life as a scientific instrument, using mercury for measuring heights and for experiments with the air pump.

However it wasn't long before the scientists realised there was a connection between the action of air pressure on mercury and weather forecasting.

The first instrument used to measure atmospheric pressure was the mercury barometer, invented in 1643 by Italian physicist and mathematician Evangelista Torricelli.

The first domestic "quicksilver weather glasses" for the home appeared in 1677 and by about 1720, domestic demand had easily outstripped that of the boffins.

As you might expect, barometers were first made by specialist companies who manufactured scientific instruments.

But once interest in them grew, all sorts of people had a go -- with varying degrees of success.

Probably most successful were clockmakers, but cabinetmakers, opticians and even gilders and picture framers got in on the act.

Notable names to watch for from the first category include the important London makers Daniel Quare and Thomas Tompion, both of whose clocks make fantastic sums at auction.

Other important makers include opticians Peter Dolland (circa 1750) George Adams (circa 1784) and instrument maker John Bird (circa 1740).

By the end of the 18th century, cities and ports were flourishing. Surveying and navigational instruments became essential to progress and the cities became recognised centres for their manufacture and that of barometers.

Another factor that boosted barometer production was a huge influx of highly qualified Italian instrument makers.

They were accomplished folk who had emigrated in search of a better life, and they were adept at glass-blowing and cabinet-making.

Their expertise was such that by about 1840, the Italians had virtually ousted English makers,

The North West was the new home to a good many of them and a substantial community of Italian barometer makers soon began to thrive.

Watch for names such as Zanetti, Fratelli, Bianchi, Bolongaro, Casartelli, Ronchetti and Solca.

Narrow stick barometers of a few inches wide and about 3ft 6ins in length dominated the scene from the earliest of days until about 1780 but remained in production until mid-Victorian times.

Cases dating from before 1800 were usually narrower than later examples and had a turned cover over the cistern holding the mercury at the base.

Rising out of this was a narrow, vertical tube through which the mercury was forced by air pressure. By 1810, this cover was replaced by a hinged box.

Reading the weather was simply a case of looking where the column of mercury stopped on a simple chart.

So-called banjo or wheel barometers –named after their shape -- on the other hand, have an indicator on a dial which operates by a float rising and falling on the surface of the mercury. As the float moves, it acts on an attached thread and moves the pointer.

Not surprisingly, the cases of both types of barometer often matched the design and decoration seen on longcase clocks of the same period. As fashion changed, so clocks changed with it and barometers followed suit.

Cases in the 1760s were usually in mahogany with satinwood inlay featuring a shell or a star. From the mid 1780s, the glass covering the dial was convex.

Regency wheel barometers had cases usually veneered in rosewood, sometimes cross-banded in different coloured wood and inlaid with brass or mother-of-pearl.

The mercury barometer was largely superseded by the invention of the aneroid barometer in 1844 (aneroid means without fluid). An aneroid is a flexible metal bellow that has been tightly sealed after having some air removed.

Higher atmospheric pressures squeeze the metal bellows, while lower pressures allow it to expand, as the Business Manager’s test proves.

Greater accuracy, smaller size, portability and cheapness of production were the reasons for its success.

Spill the mercury from a stick or wheel barometer and it is rendered useless (you might want to bear this in mind where plastic bags are involved!). An aneroid barometer has no such problems, underlining just how important a development the mechanism was.

The next time we go out to a flea market in search of a barometer, I'll be sure to take placcy bag with me.

Whether I'll find a dealer prepared to let me subject his antique barometers to the ultimate test remains to be seen.

However, don't be too deterred from buying a damaged barometer, at the right price. With the increase in interest they are currently enjoying, restoration is a good investment bet.

Pictures show: Top - This stick barometer dates from circa 1890, proving that the design proved popular through the ages. It has an ivory-backed scale and thermometer and is worth £400-600

Centre - A good mid-19th century Victorian rosewood mercury barometer and thermometer by London maker Apps, of 433 Strand. At £600-1,000, it’s out of my price bracket

Above - A later aneroid barometer and thermometer, circa 1890, in an oak case carved with acanthus leaves and foliage. It’s worth £200-300

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