Barometers Realm

This FitzRoy’s Marine Barometer, dating from the mid-20th century, is a high-quality reproduction produced by the Dutch family company H.N. Rose, which among other things manufactured replicas of historic barometer models under the trade name Roselli.

Admiral FitzRoy considered it desirable to create a form of barometer that would be as practically useful as possible for maritime purposes: less fragile in construction and more likely to withstand the constant shocks and vibrations inevitable aboard a naval vessel. British makers regarded conventional wooden barometers as insufficiently accurate due to the uneven expansion of wood caused by its hygroscopic properties. In the original FitzRoy marine barometers—also known as Gun Barometers—the mercury tube was encased in vulcanised rubber, allowing artillery fire to be conducted nearby without damaging the instrument through ordinary vibration.

The case of the instrument consists of a cylindrical brass tube, inside which the barometric tube is housed. In the original barometers this tube terminated in a boxwood cistern with a leather base; in the present replica it takes the form of a siphon tube with a small bottle-shaped reservoir attached to the lower arm of the siphon.

At both the upper and lower ends of the brass tube, threaded brass rings are screwed onto the case. At the top, a cylindrical brass housing is attached to this thread, containing a recessed compartment in which the registration plates are mounted. At the bottom, a second cylindrical brass section is screwed on, protecting the mercury reservoir.

In this replica, the registration plates are protected by curved acrylic glass and mounted on a wooden block. Both plates are made of silvered brass: the right plate bears the barometric scale graduated in London inches of mercury, while the left plate carries the standard textual weather indications. In the original FitzRoy barometers, the scales were also accompanied by the well-known “FitzRoy words,” intended to facilitate more effective weather prediction.

The left registration plate also bears the Roselli trademark and, somewhat unexpectedly, the designation London. This may have been chosen because London is more widely recognisable than Schiedam, the Dutch city associated with the Rose family company, or it may simply refer to the English barometric scale. Two further engravings—“1899” and “Nautical”—were clearly added later, most likely by a retailer. Whatever the motivation, such inscriptions are often misleading, encouraging inexperienced buyers to believe they are acquiring an original historical instrument. Auction markets remain flooded with similar replicas that are unfortunately presented as genuine period barometers and priced accordingly. Particularly notorious in this respect are so-called Portuguese barometers from Lisbon, signed with various fictitious makers’ names.

The most interesting feature of this barometer is its functional gimbal suspension. Marine barometers must be suspended in order to maintain a vertical position as the vessel moves at sea. For this purpose, they are mounted in gimbals by means of a brass arm. The gimbal consists of a free-moving ring, secured by knurled screws to the central section of the barometer frame, both front and back. The forked end of the arm supports this ring from the sides, again using knurled screws. Owing to the greater weight of the mercury cistern, the instrument naturally rotates on its supporting screws and thus continuously maintains a perpendicular orientation; in fact, it is so finely balanced that it responds to the slightest disturbance in any direction. The opposite end of the arm is attached to a sturdy mounting plate with screw holes, allowing it to be fixed to virtually any part of a ship’s cabin. The arm is hinged to the plate so that, when required, both the arm and the barometer can be swung upward.

In conclusion, this Roselli FitzRoy’s Marine Barometer stands as a carefully executed and mechanically functional reproduction of a historically important maritime instrument. While not an original 19th-century example, it faithfully reflects the practical design principles of FitzRoy’s gun barometers and illustrates how their robust construction and ingenious suspension systems were intended to serve the demanding conditions of life at sea.