Very Strange Inclinometer?

[Martin King 2Participant @martinking2]

Here we have a beautifully made mahogany inclinometer instrument with very odd features?

Approx 250mm diameter, glass fronted as shown; has a small lead weight on cord as the pendulum.

What is very starnge is that the numerals are all upside down for reading?

Is it possibly meant to be used horizontally. perhaps on a plane table or some such? Part of a larger instrument?

Has a nice ornate brass handle to the front as if it might slide into something?

No makers marks. Google lens again nothing. Would love your thoughts on this please! Cheers, Martin

[John HaineParticipant @johnhaine32865]

Clearly Australian.

[Martin King 2Participant @martinking2]

🙂

[Dave HalfordParticipant @davehalford22513]

Might be handy if you have a field gun, who knows.

[BazyleParticipant @bazyle]

The numerals are rather scratchy, not an instrument maker’s work. Perhaps added later by child or artisan copying the protractor they were familiar with but not clever enough to know or appreciate the use intended.

[peak4Participant @peak4]

I can’t imagine why, but it’s almost as though it’s designed to be viewed by looking over the top from the far side, in which case the numerals would be the right way up.

Bill

[Martin King 2Participant @martinking2]

I agree with Bill, logically that is the may to look at the figures.

Maybe the lead ball is held vertical until a required angle is set then moved to the horizontal on a plane table or similar? It does seem to lie an d retain any angle that way?? Also the two datum lines are clearly visible that way?

Still stumped!

[Robert Atkinson 2Participant @robertatkinson2]

“look over the top” inclinometers wee commonly used measure the height of trees and the like. The groove on the front of the top frame could be a crude sight line.

Robert.

[noel shelleyParticipant @noelshelley55608]

Marine use ? Noel.

[DiogenesParticipant @diogenes]

You aim it, get your assistant to put a chinagraph/crayon mark on the glass ‘there!’ and then read off the measurement..

[Neil AParticipant @neila]

It looks like an old hypsometer, used for measuring the height of trees. The additional semicircular rings are used to indicate how far from the object you are, although I can’t see any marking on the rings. Sometimes these devices had a paper chart stuck on the back with additional information for the calculation. There are some modern examples about but not easy to find.

Interesting object.

Neil

[Martin King 2]

On 6 January 2026 at 11:58 Martin King 2 Said:

… the numerals are all upside down for reading?

… meant to be used … on a plane table …

That would be my guess.  I think it’s early, and the relatively crude markings are explained by it being locally made rather than by a professional Instrument Maker.   18th Century, before Jesse Ramsden’s dividing engine (1787).

Surveys were a vital part of estate management because wealth depended on owning land.  Encroaching into next door’s property could result in violence, but huge effort went into managing tenants and their boundaries within estates.  Clinometers are needed for Plane Table surveying, and they predate Dumpy Levels and Theodolites by centuries.

I think Martin has an antique clinometer, which, to save space, was mounted under the table and read by looking down on the scale.   The later clinometer pictured below was taken on and off the table when needed, but under the table was an option.

Used something like this to map a field:

• The table was set up in a convenient corner, levelled, and then oriented North-South with a compass.
• If the field was flat, an assistant was simply sent to each of several reference points with a sighting rod.  Trees, buildings, wall ends, gateways, river banks etc.  Ancient survey reference points were often fixed by erecting a stone that are often marked on old maps.   (I’ve never found one in place.)  The distance between the surveyor and assistant would be measured with a Pole (5½ yards) or a Chain (22 yards).  A line representing that distance would be drawn on the plan with the Alidade (a rule with iron sights on the end, later a low power telescope with cross-hairs).   Enough reference points (distance and angle) would be captured to accurately establish the field’s dimensions and shape, no matter how wonky!   Repeat until the whole estate was captured, a lot of work back when The Duke of Newcastle owned most of Sussex…
• Most fields slope in two or more directions.   If the error was bad enough, the distance measured with the chain was corrected by measuring it’s slope, perhaps at several points, and applying trigonometry.

Inclinometers were also used to produce levelled plans for new buildings and to lay-out drains.  Drains are deliberately sloped just fast enough to stop water stagnating and slow enough to stop erosion.  (About 2° if my memory is right!).

Another possibility is mining, which was very common in the UK.  Lead, Copper, Zinc, Tin, Arsenic, Iron, Graphite, Fuller’s Earth, Limestone, Slate, Coal and others, until the sources were worked out.   Mining rights belonged to the surface owner, and it was important to stay within agreed boundaries.  Mineral seams tend to wander up, down and sideways, which kept mining surveyors busy, making sure distances measured at odd angles underground were accurately translated to the surface.    Initially this was about money.  Later, as more and more mines were dug and abandoned it became important to know where adjacent workings where.  If a disused mine was accidentally penetrated, it would flood the new workings with water and gas – pretty deadly, and causing enormous damage.  Ancient unmapped mine workings are still a problem in the UK.

As Martin’s example is clean, my guess is it belonged to an estate manager, was used on the surface with a plane table, and kept as a curio when more sophisticated instruments became available.   A nice collectable.

I believe Plane Tables are still used for simple purposes like mapping archaeological digs.  But builders and miners are more likely to have Dumpy Level’s and Theodolites.     Modern theodolites save massive amounts of time:  GPS positioning, no need for notebooks, human error mostly eliminated, and they do most of the maths on the spot.   Not cheap though!

Dave

 

[Nigel Graham 2Participant @nigelgraham2]

Dave: 

About 2º slope for a drain, especially a piped one, is right. It’s 1 in 40, which gives [cot 1/40 = 2.3º].

Going back even further, prior to the invention of the spirit-level, one way of testing for level was to use a large set-square with a plumb-line down the edge. Mediaeval masons used this in erecting structures like their great cathedrals. I don’t know but imagine they made the square to 3:4:5 proportions, knowing that would give the right-angle.

……

A modern version of this rather lovely old inclinometer consists of an acrylic plate holding a semicircular tube round the protractor, and containing a small ball-bearing. It is not of very high definition but accurate enough for its intended use, geological and geomorphological surveying over fairly short distances. Nature doesn’t make hill details very accurately anyway!

I have also used the ‘Suunto’ Inclinometer, like a small version of that antique one, about 50 X 30 X 12mm or thereabouts. It consists of an aluminium block with the scale rotating in a pocket behind a circular window, and with both face and edge scales calibrated to 0.5º so readable face-on or through an eye-piece in one end. You don’t see the target through that but by the other eye sighting past the instrument.  ‘Suunto’, a Finnish company, also make or made a magnetic compass to the same basic design and used in a similar way, also calibrated to half-degrees.

[Martin King 2Participant @martinking2]

Hi All,

Sometimes things just do not work out!

This did VERY well on Ebay and we packed it up carefully and sent it on to the winning bidder only for it to arrive with the glass broken! Just waiting for it to come back to issue a full refund and see if it is capable of being repaired.

That’s life I guess..

Cheers, Martin

[renardiere7Participant @renardiere7]

Bad luck!

[Nigel Graham 2]

On Nigel Graham 2 Said:

[…] A modern version of this rather lovely old inclinometer consists of an acrylic plate holding a semicircular tube round the protractor, and containing a small ball-bearing. It is not of very high definition but accurate enough for its intended use […]

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