Tradition has it that it was Robert Hooke, better known as the originator of Hooke's Law of elasticity, who first tried to quantify the relationship between the height of the mercury column in a barometer and variations in the weather. In 1670 he equipped his barometer with a float, connected by a chain to operate a pointer on a clock-like dial.
The corresponding height of the mercury column was engraved on the dial, and the word "change" inscribed at 29.5 inches; "rain", "much rain", and "storm" were inserted at half-inch intervals on the low side, and "fair", "set fair" and "very dry" on the high side. The idea became very popular throughout Europe as a "barometre monte a la maniere d'Angleterre", set up in the English way.
Nowadays an aneroid barometer is more likely to grace the typical suburban hall than one that functions by the rise and fall of mercury. The heart of an aneroid barometer consists of a number of thin hollow capsules of corrugated metal, each one in size and shape being rather like a wafer biscuit.
When the air has been removed from these capsules, they expand and contract in response to changes in the external pressure. This movement is linked mechanically to a needle, which indicates the pressure value on a dial; the dial is also likely to be inscribed in a manner very close to that devised by Robert Hooke.
The aneroid barometer is less precise in its measurements than the mercury equivalent, but it is more convenient and portable; its design is also relatively recent. As early as 1698 the German physicist Gottfried Wilhelm Leibniz had put forward the idea of "a little closed bellows that would be compressed and dilate by itself as the weight of the air increases and diminishes".
Unfortunately it was impossible in the late 17th century to manufacture a bellows that remained both flexible and airtight for any length of time. The technical realisation of the concept had to wait until 1843 when Lucien Vidie, an engineer from Nantes in northern France, produced the first instrument of this kind.
When the aneroid barometer is fitted with a system of levers linked to a pen, and the changes in pressure are revealed in a continuous line drawn upon a chart wrapped around a revolving drum, the resulting instrument is called an aneroid barograph.
Enclosed in a shining glass case on a polished mahogany stand, with its brasswork gleaming, the aneroid barograph was in its day the epitome of Victorian micro-technological achievement.