Dreweatt Neate Donnington Priory Salerooms
Lot 187
A rare George III mahogany multiple-tube barometer Baptista Ronchetti & Co, Manchester, circa 1785. The glazed break-arch case with hinged moulded door enclosing scroll border printed paper scale applied with DOUBLE BAROMETER tube consisting of two mercury columns each with bulb at the top and to each cistern linked by a similar column filled with coloured oil, above the second cistern is an open-ended narrow bore tube extension against a printed scale calibrated 0-50 over a distance of 15 inches, to the left is a Fahrenheit scale mercury THERMOMETER, the paper scale printed with vignettes of classical deities to top and signed Baptista Roncheti & Co. Fecit above arcade decoration to base, 58.5cm high, B.C. Ref. 107. Illustrated in Banfield, Edwin BAROMETERS Stick or Cistern Tube page 210. Baptista Ronchetti is recorded by Banfield 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 approximately five times.
