A RARE GEORGE III MAHOGANY CASED MERCURY AMONTONS-TYPE MULTI...

Estimate

£1,000 - £1,500

A RARE GEORGE III MAHOGANY CASED MERCURY AMONTONS-TYPE MULTI-TUBE BAROMETER BABTIST RONCHETTI, MANCHESTER, LATE 18th CENTURYThe break-arch wooden scales with stamped arched signature BAPTIST RONCHETTI FECIT and star motif above large spirit Fahrenheit scale spirit TERMOMETER to the left-hand side with readings ranging from 20 to 110 and annotations from FREEZING to SUMMER HEAT, set next to the BAROMETER with continuous tube formed with four columns, the first on the left having sealed bulb over mercury linked at the top to a second filled with oil, which in-turn is connected at the base to another filled with mercury looped at the bottom to the fourth, originally topped with oil for providing the level for reading against a scale calibrated for 0-16 inches divided into sixths and annotated with weather observations ranging from VERY DRY to STORMY, set behind a hinged glazed full height front panel with ogee moulded frame and three small brass finials.61cm (24ins) high, 14.5cm (5.75ins) wide.Provenance:The Dr. Castle Collection of barometers and other weather instruments.Baptista Ronchetti is recorded in Banfield, Edwin BAROMETER MAKERS & RETAILERS 1660-1900 as working from 15 High Street, Manchester 1785-circa 1810. He arrived in Manchester in 1785 from Tavernerio near Lake Como, Italy and sent for his son, Charles Joshua and nephew, Lewis Casartelli from Italy who joined him in partnership for a while before going their separate ways. The concept behind this 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 a lighter fluid, thus allowing the instrument to be half the size of a conventional mercury stick barometer. Amontons version used the junction of two separate coloured oils (one lighter than the other) moving against a scale behind the linking column to indicate barometric pressure. The current instrument utilises a second column of oil above the second bulb cistern to give a reading. This scale, as with full-height double tube barometers, reads in reverse and amplifies the barometric range by around a factor of five.