A fine, London made 19th century mahogany barometer, 39 inches long, 10 inches wide by John Spelzini. The frame, thickly veneered in good dark mahogany. Signed to the level plate, J. Spelzini / 11 Brooks Market. The Spelzini family made very good quality instruments in London from the early to mid-19th Century. John Spelzini is known to have worked at this address between 1830 and 1850. The glass tube in the back is intact. It is missing the plate for the thermometer. It is a great piece, ready for restoration. I really don’t know that much about these instruments, so please ask specific questions and I will do my best to answer them and provide you with any additional photos on request. Please review the images. There is no mercury included! The first published illustration of this was in Micrographia of 1665. The idea was to bend a tube into a U shape and using the mercury level in the shorter limb to record air pressure changes by aranging a steel bullet to rest on the mercury as a float, which was connected by a silk cord over a pulley to another counter balanced steel bullet. The pulley wheel was connected to a pointer that turned around over a dial. The column of mercury in the lower limb rising and falling moved the steel bullet up and down, which in turn turned the hand left and right over the dial. This type of barometer was an attempt to magnify the movement of mercury, which in a stick barometer is relatively small, perhaps a three-inch variation in Great Britain. With the larger size needle and dial three inches can be expanded to move ten times more, so changes are more readily noticeable. The design however did not take off very easily and whilst a number of wheel barometers were made in the mid 1700s the normal wheel barometer that one sees today are those of traditional banjo shape from around 1780 onwards. They are enclosed in a cabinet made case and the siphon tube is enclosed behind a door. Whilst the design is almost the same as Robert Hookes’ the cases vary in wood, inlay and decoration. These type stopped being made when the aneroid barometer took over around 1910. The item “Antique Mahogany Banjo Mercury Wheel Barometer J. Spelzini London c. 1840″ is in sale since Thursday, July 23, 2015. This item is in the category “Antiques\Science & Medicine (Pre-1930)\Scientific Instruments\Barometers”. The seller is “lordrandolph” and is located in Dallas, Texas. This item can be shipped to North, South, or Latin America, to all countries in Europe, to all countries in continental Asia, to Australia.
- Maker: J. Spelzini / 11 Brooks Market
- Original/Reproduction: Original
