Antique Pocket Barometer with Very Unusual Double Fusee by Elliott c1870 – SOLD
Pocket barometer having 2¾” silvered engine divided dial with barometric range from 28 – 31 inches of mercury, with divisions at 100th of an inch. Standard meteorological terms: “Stormy,” “Much Rain,” “Rain,” “Change,” “Fair,” “Set Fair,” and “Very Dry.” The upper portion marked “Compensated,” the lower signed by the maker “Elliott Bros, 449 Strand, London.” Fine blued steel pointer, rotating bezel with pin index, bevelled glass.
The very unusual movement having an additional amplification stage incorporating a second fusee (essentially a twin-fusee system). Bi-metallic compensation to primary lever, steel ‘C’ spring, raised upon a steel chassis.
All contained within a drum form case with compensation port to verso at 4 o’clock. Suspension pillar and ring.
This instrument presented some interesting problems: a combination of original and possibly later work. The additional fusee going to greater amplification was designed to provide for a wider scale and thus the apparent accuracy of the instrument – these important components are undoubtedly original; it would appear that the capsule and primary lever (supporting the ‘C’ spring) may be later. Upon dismantling, it became immediately evident that the adjustment screw and corresponding thread within the primary lever were lacking – these were replaced employing original parts. The thread is left-handed and of an early pitch and form. This was removed from a contemporary instrument, turned to a small cylinder and silver soldered into the existing brass primary lever. The capsule was repositioned and a cut out formed into one of the primary lever support posts – this was necessary since the capsule evacuation point covered the chassis securing screw in its as found position. Both suspension ring and post were made and replaced since these were missing.
A great deal of workshop time has been spent on this instrument, in essence because it is a significant development in the design of the aneroid barometer. It is not certain as to why precisely both capsule and primary lever are early replacements; it is likely though that a failure in the primary lever or possibly the ‘C’ spring pierced the capsule. This type of failure is not unknown – the loads in tension placed upon these components are relatively high, metals age as the crystal structure changes and they become embrittled. In some later instruments, design changes are incorporated to prevent damage to the capsule should a similar failure occur.
Now presented in good working order and condition, retaining some original finish to the lacquered case, the dial very crisp. An unusual and interesting item.
Dimensions: 2¾” diameter x 1¼” deep
Stock No: PB0663