A MAHOGANY-CASED AMONTONS-TYPE MULTI-TUBE WALL BAROMETERUNSIGNED, LATE 20th CENTURYThe moulded break-arch mahogany panel applied with continuo tube formed with four columns, the first on the right having bulb over mercury linked at the top to a second filled with red-stained oil which in-turn is connected at the base to another filled with mercury looped at the bottom to the fourth topped with oil providing the level for reading against a paper scale calibrated in enlarged reversed barometric inches divided into tenths ranging from 27.9 to 31.3.The panel 61cm (24ins) high, 14cm (5.5ins) high.Provenance: The exhibition collection of Barometer World Meum, Merton, Devon.The concept behind this type barometer is to make the instrument more portable by reducing its size. In 1688 a Frenchman, Guillaume Amontons published a design for a multiple tube barometer where the mercury column had been split into two, placed side-by-side and linked by a column of lighter fluid, th allowing the instrument to be half the size of a conventional mercury stick barometer. Amantons barometer ed the junction of two different coloured oils (one less dense than the other) to provide datum for reading against the scale whilst the current lot utilises a single coloured oil above the second bulb of mercury to provide the reading. The scale, as with full-height double-tube barometers, reads in reverse and is amplified by around three times.