A very good five-glass brass barothermograph by Negretti & Zambra, London No 2698 c1905

The barometer driven from a seven-cell pressure sensing unit, the primary lever with bi-metallic compensation, aluminium arm mounted to spindle with gain adjustment, nib pressure adjustment on a machine screw, chassis mounted calibration stem. The 3¾” diameter x 7¼” high recording drum with eight-day platform escapement movement, and having serially numbered matching sun wheel.

The thermograph driven from an alcohol filled Bourdon tube supported on an open oxidised and lacquered frame over a sub-chassis with calibration stem raised on three tapered columns, aluminium recording arm mounted to spindle with gain adjustment, the assembly constructed within a two piece single side supported frame.

The whole raised over a full length chassis stamped “2698,” arrestor bar with side lever, ink station with bottle and dipper, attached ivory plate bearing the maker’s name, “Negretti & Zambra, London.”

Presented within a five glass, bevelled top glass, medium oak case, hinged lid and frieze drawer.

Condition: The subject of a complete re-build, conservation, and calibration under laboratory conditions.

This instrument presents very well indeed, original in all respects save replacement recording arms and nibs. The brass work retaining virtually all its original lacquer, pressure sensing capsules exceptionally good with minimal external signs of deterioration.

The oak case retaining a very good proportion of original finish with good overall shine, though generally faded due to sunlight. The frieze drawer with some losses to extreme left hand side. The glass panels intact though with some minor abrasions.

The instrument works extremely well, with both instruments demonstrating unexpectedly good resolution.

Comments: These early pattern instruments are very rare and extremely collectable. Not only do they offer really very good aesthetic appeal, but this one in particular works exceptionally well.

Hand-built, with much depending upon the setting up of the instrument, the revered name Negretti & Zambra produced good instruments to a certain standard – not the best that could be had at that time but, with their wide range and marketing, the company achieved a high measure of success. This instrument is such an example. It was badly set up from the start, perhaps an exception but probably more a reflection of companies competing hard to get their products to market – no manufacturer could possibly spend the time in set up and tuning that I undertake. It nows functions very well as a result of that investment on my part.

Featured in the Negretti & Zambra catalogue of c1910, as stock no. 91, this barothermograph would be very hard to beat for rarity, condition and function. Very much a collector’s piece.