Antique pocket barograph constructed in brass and steel with nickel-plated parts, having twin chart transport rollers, the outer roller with detensioning lever enabling the easy loading and removal of charts.
The well-engineered mechanism comprising a clockwork motor and barometer driven by twin 35mm diameter capsules tensioned on a coil spring with axial calibration screw, the signal transmitted through a rocking shaft with counter-balance to a counter-balanced recording arm set on vertically opposed pivots with base-mounted hair spring, spring bias adjustment on a square.
The clockwork mechanism set between polished steel plates with platform balance and going barrel driving geared reduction train with power to chart transport rollers, causing one complete chart rotation every six hours, and recording arm control having rising and falling gate causing inked chart mark on a 30 second cycle.
The nickel-plated mechanism cover with the “JR” monogram of Jules Richard, “Made in France,” and “Brevette, SGDG,” and having three control points: the first, marked “1,” a three-position slide control with “A” denoting normal service or operating position, “B” the arrested position with the arm away from the paper to allow changing of the recording chart, and an arrow indicating the mid-position which allows free and unrestricted movement of recording arm as required for calibration; the second, marked “2,” the calibration square; the third, “3,” the clockwork regulation control. The lower left struck with instrument serial no “1471” and “6H,” denoting a six-hour chart cycle. The lower right struck type “F” and “7,000 F,” denoting a full scale deflection of 7,000 feet. Maintained to the chassis on twin slotted blued round nuts.
All contained within its steel and timber faux black leather covered case with oblong bevelled glass viewing port. Top hinge with button release and snap closure.
The pocket barograph with its correct mahogany case divided internally into two principal compartments, the left hand fitted for the recorder with crimson felt lining to base, the right hand with hinged cover having nickel-plated button and ivorene retailers’ plate marked “Negretti & Zambra, London,” twin compartments below fitted for papers, ink and sundries. Twin plated swinging catches to front. Serviced, in good working order and supplied with correct key, spare original recording papers, joiner and ink.
A fascinating instrument and a study in miniaturization. Rarely seen, this one is unusual for its excellent condition and completeness. Of the three versions produced for the English market, this is type F, designed to record altitudes to 7,000ft, for use by tourists, engineers and balloonists.
The charts are manufactured from particularly thin paper to allow easier transport over the narrow diameter transport rollers. The paper is joined into a continuous loop, the two ends overlapped and sandwiched between two flat metal strips secured with a long pin.
The barometric mechanism is tensioned on a coil spring – although almost all manufacturers moved from the coil spring of Vidi’s original patent to the C-spring, Jules Richard maintained use of the coil spring, perhaps because the characteristics of this design, in certain respects, are superior to the later design.
Fully serviced, conserved and correctly set-up, this is very much a collectors piece.
Dimensions: 4½” long x 3¼” wide x 1½” deep (pocket barograph); 7″ wide x 5½” deep x 2″ high (mahogany case)
Stock No: BG0851