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A319-26 · Mercury
c.1890
Object Overview
An exceptionally rare and unconventional instrument: a French Atmos — Barometer, circa 1890, made — on the balance of the evidence — by the Paris workshop of Jules Richard.
Nothing else in its class looks like it. Where a conventional aneroid hides its movement behind a dial, this one puts the whole of it on display: turned brass pillars, knife-edge bearings, a profiled beam, a steel helical spring, a stack of corrugated Vidie capsules — all mounted in the open on a substantial brass base and enclosed in a fully glazed mahogany case. The result is less a meteorological accessory than a display case for a barometric movement, in which reading the pressure and demonstrating the principle are one and the same act.
The instrument is unsigned. The attribution therefore rests not on a maker's mark but on an accumulation of correspondences in those elements a workshop made or commissioned for itself and carried from model to model: hardware, the joinery of the case, the turned profile of components, the overall architecture of the instrument. No single feature settles the matter; the weight lies in their combination.
external coil spring
brass, glass, nickel silver, nickel-plated brass, silvered brass, steel, wood
The instrument invites comparison with the recorders of Jules Richard and Richard Frères, and specifically with an example in the foundation's collection. One point of correspondence is the carrying handle: a flat rectangular backplate, two spherical boss-mounts, and a bail with a distinctive double "swan-neck" bend — first outward from the boss, then up and horizontal. On the Richard instruments the proportions of backplate to bail agree, as do the seating of the bosses on their cylindrical collars, the radii of the bends, and the way the bail meets the boss from the side rather than from above.
A second point is the joinery. The case uses a through, straight-sided finger joint (box joint). The pitch of the fingers agrees, as does their width relative to the thickness of the wall, and the fact that the joint is left exposed and unconcealed — this on an instrument whose glazing frame is otherwise moulded and carefully finished.
A third point is the turned pillars, executed to a single profile: a broad bearing collar at the foot, a shaft tapering smoothly upward, a distinct groove beneath the upper face, a flat landing for the bearing block. The turner's hand — the placement and depth of the grooves, the ratio of collar height to shaft diameter — agrees.
The principal conceptual argument is the architecture itself. The layout of the "Atmos" has no parallel among barometers, yet it reproduces the layout of a barograph in full:
Conceptually this is a forerunner of the barograph, or a transitional form, still without the clockwork drum and performing an indicating rather than a recording function. At the same time the "Atmos" retains from the traditional aneroid two assemblies a barograph does not have: a pair of pointed pillars with knife-edge bearings carrying the massive lever, and a helical spring on its own column against which the long arm bears. This is precisely what one expects of a hybrid: barograph layout, barometer mechanics.
The kinematics of the "Atmos" — a stack of aneroid capsules, a beam on knife-edges, a long pointer on a large arm, an external helical spring on its own column, a screw zero adjustment — fall entirely within the constructional repertoire of Jules Richard's Paris workshop as attested by two of his patents: that of 5 December 1876 (improvements to the construction of aneroid barometers) and no. 139,070 of 26 August 1880 (recording barometers). Neither patent describes the "Atmos", and no known claim protects it. Its significance lies elsewhere: it represents an intermediate form between the traditional aneroid and the barograph — the mechanics still barometric and of the early Vidie type, while the layout, the long-lever transmission and the glazed wooden case already constitute the type-form that became canonical for recording instruments after the 1880 patent. The place occupied by the "Atmos" scale plate was taken by the drum with its clockwork concealed inside.
Until that point the traditional aneroid lived in a round brass case with dial and bezel — a form inherited from clocks. An instrument with a long straight pointer cannot be accommodated in such a form at all: a long arm requires a rectangular volume. The "Atmos" solves this with a glazed wooden box and a carrying handle — a form previously unknown among barometers. The 1880 patent shows what followed: the clockwork is moved inside the drum, drum and movement become a single unit independent of the base, and the whole assembly occupies the left half of the box — exactly where the "Atmos" carried its scale plate. The pointer receives a pen and begins to write on paper instead of indicating against an engraved arc.
The typography of the Richard instruments belongs to a single repertoire of letterforms:
The mark BREVETÉ S.G.D.G. and the inscription MADE IN FRANCE independently confirm French origin.
Edwin Banfield mentions the Atmos—Barometer briefly in his book, dating it to 1880. The instrument he illustrates differs from the present barometer in certain respects. First among these is the protective glass with a broad bevel, characteristic chiefly of early production. The scale plates of Banfield's barometer are also arranged differently — they form a kind of oval frame resembling a photograph mount. The inscription "Made in France" is likewise absent. The requirement to indicate country of origin on imported goods was introduced by the American McKinley Tariff Act of 1890 (section 6, in force from 1 March 1891); the British Merchandise Marks Act of 1887 required an indication of origin only where foreign goods bore the name or trade mark of a British firm. The internal movement, meanwhile, is entirely identical. Taken together, these features date the present barometer to approximately 1890.
The Atmos-Barometer is accordingly attributed to the workshop of Jules Richard on the strength of correspondences in the carrying handle, the finger-jointed case, the turned profile of the brass pillars and the overall layout of the instrument when set against a dated barograph from the same workshop, together with the shared repertoire of engraved letterforms. The attribution is probable, not documented.
The instrument's name is engraved as ATMOS — BAROMETER — with a dash — and this is not a peculiarity of English grammar but a proprietary compound name devised by a French maker: "Atmos" functions not as an ordinary English modifier but as a proper name, a trade designation for a type of instrument, with the dash joining it to the generic word "Barometer." It is telling that this form recurs across the few known examples (including those with English, Czech and German scales) and on both plates of a single instrument.
Had the maker simply wished to write "atmospheric barometer" in English, the natural form would have been "Atmospheric Barometer." Here, "Atmos — Barometer" means "a barometer of the Atmos system or type": morphologically, a new compound name for the object is created. "Atmos," then, is a proprietary commercial name for the instrument or system, coined from the Greek ἀτμός (atmós) — "vapour, exhalation" — by way of the notion of the atmosphere.
It is not an abbreviation of "atmospheric" but a word in its own right, meaning something like: instrument of the atmosphere, instrument for measuring the weight of the atmosphere.
The name is remarkably well chosen for an international market: short, scientific in sound, and taken almost identically by a Frenchman, a German and an Englishman.
The barometer's case is a rectangular mahogany display box with a polished surface, standing on four flat transverse plinth feet. The side walls are joined to the top by a through, straight-sided finger joint, left exposed and forming a conspicuous part of the object's appearance: the finger ends run in an even comb along the upper edges.
The front is glazed across its full width with flat mineral glass set in a moulded frame. The case is entirely closed; no access to the movement is provided.
Above sits the carrying handle already described: a flat rectangular backplate, two spherical bosses, a bail with a double bend.
The instrument has no dial in the ordinary sense. The interior is divided vertically: the lower third is occupied by the movement on its brass mounting plate, while the upper two thirds remain empty — this is the working volume through which the long pointer travels.
In place of a dial there are two flat vertical plates set at the back of the case and facing the glass:
Both plates are of silvered brass. The scales, figures and inscriptions are cut with a graver and filled with black wax, giving high contrast at a shallow depth of stroke.
The barometric scale is laid out as an arc, its convex side to the left, and is calibrated in London inches of mercury over a range of 28–31 inches. The figures 28, 29, 30, 31 are engraved on the inner side of the arc — the side facing the movement.
Each inch is divided to twentieths; the divisions form a distinctive two-row "ladder" pattern of small rectangles running the length of the arc.
On the outer side of the arc, to the left, the scale carries a verbal weather indication in five standard terms, arranged along the arc from bottom to top:
STORMY — RAIN — CHANGE — FAIR — VERY DRY
The inscriptions are in narrow capitals of the same letterform family as the figures.
At the foot of the plate, along its right edge, the words ATMOS — BAROMETER are engraved vertically.
The right-hand plate, raised on its own turned brass pillar at the back of the case, carries two thermometers set as two opposed arcs which together form a smooth lyre:
Both are made as curved glass tubes following the arc of the engraved graduations; the bulbs are brought close together at the centre of the plate.
The upper part of the plate carries the instrument's name engraved: ATMOS — BAROMETER.
Beneath the name is a decorative separator, an asterisk between two dashes: «— * —»
This is a dingbat separator, kin to the asterism and to typographic fleurons. An ornamental divider beneath a heading was general European compositors' practice in the nineteenth century, as usual in Paris as in London or Vienna.
At the foot of the plate, in the corners: on the left, BREVETE S.G.D.G. (breveté sans garantie du gouvernement — patented without government guarantee, under the French law of 5 July 1844); on the right, MADE IN FRANCE.
Besides the principal steel indicating pointer, the instrument carries a second — an elegant brass trend pointer. It is not connected to the movement and does not move of itself: its purpose is to record the position of the main pointer at the moment of the last reading, so that at the next glance the direction and magnitude of the change in pressure can be seen.
The pointer is made from thin brass strip and is ornamented at its centre with a pierced openwork motif in the form of an elongated loop running into a stylised finial.
It is set by hand from outside the case: a small lever projects from the right-hand side wall, connected to the pointer's arbor. Moving the lever up or down rotates the brass pointer, allowing it to be aligned with the current position of the indicator without opening the glass.
The whole movement is assembled on a rectangular brass mounting plate screwed to the floor of the case. The plate carries everything without exception: the capsule stack, the beam, the pillars, the spring, both scale plates and the pointer-arbor assembly. Lifted out of the box, it forms a complete instrument in its own right — a circumstance material to understanding how the design was conceived and how it relates to recording instruments, where a plate of the same kind serves as the base for the drum and the clockwork.
The sensing element consists of two corrugated Vidie aneroid capsules of about 60 mm diameter, suspended from a separate turned brass pillar passing through their centre. The pillar is screwed into the mounting plate and carries the capsules upon itself, leaving an open space beneath the lower capsule.
The upper membrane of the upper capsule is connected by a short vertical link, pivoted at both ends, to a massive brass beam — an arrangement that spares the membrane any lateral loading as the beam swings.
The beam, in effect a double-armed lever, is a massive brass bar lying across the whole movement. It rests on turned brass pillars through knife-edge bearings. This is the classic solution of precision mechanics — rolling contact in place of sliding friction, freedom from backlash, immunity to the wear of pivots.
The beam is profiled: its outline carries shaped cut-outs and flowing swells. This is not ornament but balancing — metal is removed where its mass would work against sensitivity and left where stiffness in bending is needed.
The long arm of the beam extends well beyond the capsule assembly and bears on a steel helical spring fitted over its own turned column. The spring is the sole elastic counterweight to atmospheric pressure; it balances the weight of the atmosphere acting on the stack of aneroid capsules.
Zero is set from below the instrument. A screw accessible through the base alters the tension of this helical spring, thereby shifting the whole position of the beam and consequently of the pointer along the scale.
Here the design parts company with both the traditional aneroid and the barograph, and the divergence is worth setting out in detail, since it constitutes the instrument's principal constructional rarity.
How an ordinary aneroid is built. The movement of the capsule is transmitted to a cast-iron traverse (a double-armed lever); from its long arm an oblique link runs to a bell-crank turning on pivots; the vertical arm of that crank is connected to the pointer arbor by a fusee chain wound round the arbor, while a hairspring provides the return and takes up backlash. The bell-crank on its pivots, the chain and the hairspring are assemblies going back to the first Vidie movements and surviving in aneroids to the present day virtually unchanged.
How the "Atmos" is built. It contains none of this. The long arm of the beam, bearing on the helical spring, continues further to the right and connects by a short link directly to the pointer arbor carrying the long indicating pointer. The arbor is mounted in a separate brass forked bracket on the right-hand turned pillar; visible within the fork are the steel axle, a clamping screw and a sprung plate taking up the clearance mechanically.
Instead of converting linear travel into rotation through a chain, the design uses a direct lever articulation: the swing of the beam, acting through the link, imparts a small angle of rotation to the arbor, while the whole of the required reading span is obtained not by a gear ratio but by the length of the pointer itself. The pointer here works as a continuation of the lever, not as an indicator mounted on a reduction train.
Dispensing with the chain and the hairspring removes two sources of hysteresis and lost motion, but in exchange demands closer tolerances in the articulations and makes the instrument sensitive to levelling: a massive beam on knife-edges responds to any tilt of the base. Hence the flat plinth feet of the case and the weight of the brass base.
On the whole of the evidence, the pointer-arbor assembly should be regarded not as a simplification but as an independent solution lying outside the main line of the aneroid's development. The mechanics meanwhile remain of the early type — an external helical spring on its own column, an open lever transmission — while the layout as a whole already anticipates the one that became settled practice for recording instruments.
The value of this instrument lies not in rarity as such, though the known examples are indeed few, but in the fact that it occupies an intermediate position of a kind that does not usually survive: transitional forms are either displaced or developed into a finished state, losing the traces of their origin. The "Atmos" has come down in precisely that transitional condition.
On one hand, its mechanics belong to the early period of the aneroid barometer: an external helical spring, a massive beam on knife-edges, an open lever transmission — solutions going back to the first Vidie movements. On the other, its kinematics already abandon an assembly that has survived a century and a half in aneroids: there is here neither fusee chain, nor hairspring, nor bell-crank on pivots. The transmission runs from the beam straight to the pointer arbor, and the required reading span is taken from the length of the pointer rather than from a gear ratio.
It was the long pointer that carried the instrument out of the round brass case and into a rectangular wooden box — a form previously unknown among barometers and subsequently canonical for barographs. By replacing the scale plate with a drum enclosing its own clockwork, and the indicator with a writing pen, the workshop arrived at a recording instrument that would define the appearance of meteorological technology for the century to follow. The barometer thus turns out to be at once a measuring instrument, a working model of its own principle, and a kind of forerunner of the classic barograph — not chronologically, but conceptually.
The attribution to Jules Richard's workshop remains the most probable: there is no maker's mark on the instrument, and no known patent describes it; yet the correspondences are too numerous, and lie across too many different crafts — the casting of hardware, joinery, brass turning, the constructional repertoire of the mechanics — to be explained by a shared supplier.
This Atmos — Barometer stands as an independent and thoroughly unusual branch in the development of the aneroid. Its proprietary name, its exposed mechanics, the almost architectural organisation of its interior space and the rare system of direct pointer drive make it not merely a curious variant of the barometer but an eloquent monument of French precision instrument-making at the close of the nineteenth century.