For sale, a Victorian long range glycerine barometer by Negretti & Zambra London
This hugely scarce example is comprised of a rectangular oak case with architectural pediment and base. It has a dome topped glazed front with an opaline glass painted scale behind which runs almost the full length of the barometer measuring 28 to 31 inches of barometric pressure. The right side has the detailed numerical scale whilst the opposing side contains standard weather indications. The top of the scale is painted with the maker’s name, “Negretti & Zambra, Opticians, London”.
The coloured glycerine filled tube to the centre has a brass collar surrounding the tube which may be used to mark the current locations of the liquid and can be hand adjusted at the right hand side.
This ingenious stick barometer was devised by Negretti and Zambra in order to make accurate barometer reading easier for the observer. This strive for user friendly weather forecasting culminated in their later and renowned weather forecasting patent instruments. This early development was intended to remove the pain of complex Vernier measurements against the normally small scales of the domestic barometer and although it eventually proved to be less accurate than its predecessors as a serious scientific instrument, it certainly remains accurate enough for common domestic use. It also rivals most examples for its sheer decorative presence.
The following explanation should be read in conjunction with the Negretti catalogue image provided but it should be noted that to my knowledge, this exact design was never presented in any of their catalogues. It is the only example of this design that I have ever encountered:
“The Longe range or open scale barometer consists of a glass tube of the syphon form; one side of the syphon A (or closed end), being about 33.5 inches long, and the other only a few inches in length. To this short end is joined a length of glass tubing B, of a much smaller internal diameter; both tubes are of equal length, the smaller one being open at the top. The large tube A, is filled with quick silver, and the small tube B is partly filled with glycerine, a fluid many times lighter in specific gravity than quick silver; the rising and falling of the quick silver column in the large tube having a lighter fluid to balance, and that dispersed over a larger space by reason of the difference in the diameter of the two tubes, a longer range is obtained due to the unequal capacity of the two tubes and the difference in the specific gravity of quick silver and glycerine.
The range of these barometers is from six to ten inches to the inch of an ordinary barometer. A hundredth of an inch can easily be observed without the use of a Vernier. It is a most interesting instrument, as from the extremely extended scale the slightest variation is plainly visible. The actual size and form is about that of an ordinary barometer”.
Negretti & Zambra were a leading name in the production of meteorological and scientific instruments and had a company history dating back to 1850 although their parents were amongst those Italian emigres that bolstered the British meteorological instrument making industry at the turn of the century.
Throughout their long and esteemed history they exhibited at British and international industrial fairs and became makers to both Queen Victoria and Edward VII. Owing to changes in the business, the firm ceased the public retailing of scientific instruments sometime around the late 1960’s and continued with a focus on the aviation industry in numerous guises until its eventual liquidation in the year 2000. They are today perhaps the most collected of the scientific instrument firms which bears testament to the quality of their work.
A scarce, interesting and very beautiful stick barometer by the foremost makers of meteorological instruments of the Nineteenth Century. The barometer remains in good working order although it does have some historic but stable cracks to the glass scale on the right hand side to the base and about half way up where the mounting screws and the movement of the wood over time have created pressure on the glass, however these are very forgiveable given its extreme rarity.
The barometer is somewhat difficult to date given the lack of catalogue evidence, Negretti produced the long range barometer from around 1870 through to the turn of the century but given some of the details on the scale this fine piece would date to the earlier period of their production.