Barograph having special movement with four jewelled pivots raised upon four hexagonally based and terminated tapered pillars over a full length acid-etched chassis with fluted borders, having ink station, bottle with dipper, recording arm arrestor bar, pen setting knob and marked ““Regent” Jewelled Movement.” Single volume pressed and hardened steel sylphon pressure sensing capsule with zero adjustment dummy diaphragm below, polished steel cross shafts with finely executed linking levers. The barometer section comprising: drum-form body enclosing barometer arbor and hair spring assembly, semi-circular dial calibrated in inches of mercury with a range from 28 – 31, annotated with standard meteorological terms “Stormy, Rain, Change, Fair,” the upper part signed by the maker “Negretti & Zambra, London,” the lower right extremity with “N&Z” logogram, and opposing end bearing the instrument no. “R/20637,” blued and counterbalanced steel pointer. Swinging gate recording arm with original Negretti & Zambra precision nib.
3⅝” diameter recording drum, spring clip paper retainer, enclosed clockwork having conventional platform escapement, captive winding key, the top cover with regulation port marked “S” and “F,” further marked “179H” (just over seven days duration), lift off spun dust cover, the assembly maintained on a vertical axial steel shaft with captive sun wheel to base. Lacquered mahogany case with frieze (chart) drawer below, five glass lift-off cover.
Occurring infrequently on the market, these instruments were Negretti & Zambra’s flagship barograph for the domestic market, and far superior to any other readily available instrument at the time. Based around the Negretti & Zambra-perfected sensing capsule or sylphon, essentially a single volume body with one evacuation port, the material and structure for which was selected after extensive research in the early 1920s. This new pressure sensing body benefited from an almost complete absence of hysteresis and a high degree of linearity.
Coupled with a highly-engineered movement set on jewelled pivots, this made for a very superior instrument indeed. Production probably began around 1925 and certainly carried on into the 1970s. This instrument is an early one, the case annotated no. “14.” This does not necessarily suggest this was the 14th of these instruments made (though this is possible) – it may relate to the case maker’s inventory.
The standard of engineering design and execution found in this instrument is second to none. The instrument encompasses almost every conceivable refinement for such instruments, not least being the swinging gate type recording arm, a design that may be found in some of the better barographs. This system ensures consistent pen pressure in the vertical plane and allows for the possibility of some eccentricity in the drum or run out in the spindle. This does mean, though, that the instrument must be placed on a perfectly level surface in order that the original bias settings are preserved.
The mahogany case with minor marks and impressions, the glasses chip-free and secure, minor scratches to top light, the brass work clean and vibrant, the barometer dial with obvious ageing. The barometer movement in very good and original condition, the recording drum free of dents or damage. The clockwork running well, the balance with good amplitude. Overall crisp with wonderful aesthetic properties.
The subject of an extensive overhaul, the movement completely re-built to exacting standards, this is a completely original example. Having been properly calibrated, the resultant pen traces bear testament to the fine properties inherent in this design, with very smooth and highly sensitive recording, and near perfect progression.
This instrument does appear as different and, with its unusual acid-etched chassis and some component parts, it is – it is a truly beautiful piece of engineering, and arguably the ultimate expression of the basic design in its class.
Dimensions: 16½” wide x 9½” deep x 7½” high
Stock No: BG1337