Barometers Realm

This Fisherman’s Aneroid Barometer, circa 1880, serial number 414, was supplied by Negretti & Zambra for the Royal National Lifeboat Institution (RNLI). The instrument was specifically designed to provide a reliable aneroid barometer in a compact format suitable for use aboard small fishing vessels and coastal craft, where the use of a mercury barometer was impractical.

The barometer is housed in a compact and robust cylindrical case. The body is made of bronzed metal, finished in black, giving the surface a deep, dark tone while simultaneously providing protection against corrosion in conditions of high humidity. The construction is fitted with two mounting lugs—one at the top and one at the bottom of the case—intended for secure attachment to a ship’s bulkhead, preventing displacement or damage during heavy motion at sea.

The front is protected by a brass bezel fitted with a thick plate glass, faceted at the edge. This type of glass not only increases the mechanical strength of the assembly but also creates additional optical depth, while protecting the dial from impacts, salt spray, and direct contact with water.

The dial is executed in vitreous enamel on copper: a glassy enamel layer is applied to a copper plate and then fired at high temperature. This process produces a dense, chemically stable surface with a characteristic smooth, slightly glass-like finish. Such construction was specifically employed in instruments intended for use in harsh environments, as enamel is highly resistant to moisture, salts, and temperature fluctuations. A dial of this type is designed for long-term durability, even under direct exposure to water.

The barometric scale is arranged concentrically and spans a range from 26 to 31 London inches of mercury (inHg), with a high degree of precision—graduated to increments of 0.05 inches. Instead of the traditional and often imprecise verbal weather indications, the scale incorporates a condensed and more practical interpretation of Admiral FitzRoy’s forecasting rules, linking pressure changes with wind direction and character. One traditional term from the earlier system is retained—changeable—positioned at approximately 29.5 inches, serving as a transitional element between the older descriptive system and the more analytical approach.

In the lower part of the dial, alongside the name Negretti & Zambra and the instrument’s serial number 414, appears the designation of the English maritime rescue organization, the Royal National Lifeboat Institution (RNLI). The inscription “Issued by the Royal National Life Boat Institution” reflects the role of the RNLI as distributor and certifying body within its maritime safety program, ensuring specification and inspection standards, and distributing instruments through its network of local stations and honorary secretaries.

The Royal National Lifeboat Institution was founded on 4 March 1824 at a meeting held at the City of London Tavern (Bishopsgate), on the initiative of Sir William Hillary and his associates, including Thomas Wilson and George Hibbert. Historically, the RNLI was concerned not only with rescue operations following shipwrecks but also with the prevention of maritime disasters. This included the installation of barometers at lifeboat stations and the subsequent program of supplying fishing vessels with aneroid barometers at subsidized prices.

In 1860, an issue of The Life-Boat reported the RNLI’s intention to install barometers at lifeboat stations for early storm warning; the publication included a letter from Robert FitzRoy of the Board of Trade (Meteorological Department), confirming cooperation and the practical aspects of supply and use. In June 1882, a formal scheme was introduced under which the RNLI began to issue and supply reliable aneroid barometers to owners and captains of fishing vessels and small coasters at significantly reduced prices, with Negretti & Zambra and Dollond & Co. named among the manufacturers.

Barometers bearing RNLI references on the dial represent a serial production associated with a long-running program aimed at the widespread provision of high-quality aneroid barometers to the fishing fleet.

The operation of the Fisherman’s Aneroid Barometer is ensured by a reliable conventional movement: the aneroid capsule is made of German silver and tensioned by a C-shaped steel spring, stabilizing its response. Motion is transmitted from the capsule to the pointer arbor via a fusee chain, a solution characteristic of high-quality English aneroids of the late nineteenth century.

Taken as a whole, this barometer represents a functionally refined and structurally robust marine instrument, in which utilitarian accuracy is combined with carefully considered protection of all components against environmental exposure.