A rare and important Whiteside-Cook’s Sea Level Aneroid Patent No 14424 by Negretti & Zambra, London No 20721 c1910

Large Whiteside-Cook’s Patent pocket barometer having 2¾” silvered and die struck dial with return, the outer barometric scale calibrated in inches of mercury with a range from 21” – 31” divided down to 1/20th, the upper part marked “Whiteside-Cook’s Sea Level Aneroid, Patent No 14424,” the lower part signed by the maker “Negretti & Zambra, London,” serial no. “20721,” the “N&Z” logogram, and “Compensated.” Blued steel pointer, bezel driven thorn index at reflector ring, bevelled glass.

The conventional first quality Vidie pattern movement driven from a single nickel alloy 1¾” capsule tensioned on a C spring. All contained in a special three part drum form case, the bezel with engine turned finisher, the central section marked in feet divided down to 20’ with a range from 0 – 10,000’, the verso with marked triangular index to side and calibration port. Post with crown locking altitude adjustment, suspension ring.

Presented in its original burgundy leather over timber, green velvet and silk lined case, the lid inner marked in gold block “Negretti & Zambra, Scientific Instrument Maker, London” with “N&Z” logogram. Snap closure on a button release.

Condition: The subject of a full service, conservation, and calibration under laboratory conditions, see performance chart from dynamic test. The movement working well across the scale with acceptable levels of accuracy for domestic purposes, sensitive, responding well to pressure change. 

The dial crisp and clean with minor mark at centre, the bevelled glass chip free, two minor scratches. The brass case retaining virtually all its original lacquer, scratch to verso, light wear and some minor oxidation.

All mechanical parts working well, the bezel and verso rotating freely with correct resistance, the verso crown operated lock working positively. Small repair to fine chain.

The travel case sound and with good colour, the lid silk faded, the hinge replaced, small piece of leather added and minor repair above button.

Overall, crisp and clean and in very good condition.

Comments: This is one of the super rare but very important aneroid barometers that very rarely surfaces. Although this is to all intents and purposes a conventional aneroid pocket barometer, the development that Whiteside-Cook added became accepted generally as one of the most important aspects of functionality of the better and some mainstream instruments.

The really big advantage this instrument offered was the ease with which an accurate pressure reading may be made once the station height had been established. The added advantage of this system is that the instrument always remained in calibration, i.e. the parameters of the movement remained the same as opposed to turning the adjustment screw on the verso which perceptibly changes ratios within the movement.

This system of course was built into the Negretti & Zambra Weather Watch and its bigger and more impressive brother, the Forecasting Aneroid. Short & Mason used it widely in their Stormoguides, along with many other makers and instrument types.

Absolutely pivotal to the completeness of any collection.