slide rule
Enable an AI agent to recognise a slide rule, assess its computational and physical readiness, and decide which calculations, checks or handling actions are appropriate.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise a slide rule, assess its computational and physical readiness, and decide which calculations, checks or handling actions are appropriate.
A slide rule is a mechanical analog calculator that represents real-valued functions as lengths on logarithmic and allied scales on a stator, a sliding bar and a cursor, so that multiplication, division, roots, powers and many trigonometric and exponential evaluations are performed by aligning marks rather than by discrete arithmetic.
It can be Identify and explain the observed computational scales using matching documentation.; Set inputs and read approximate results for operations supported by the instrument.; Transfer a reading between scales using the instrument's cursor, pointer or index arrangement.; Check alignment and computational behaviour against selected known results.; Assess whether binding, slipping, damaged markings or reference defects restrict use.; Recommend documented handling or adjustment steps appropriate to the mechanism and materials..
Distinguishing features
Calculations depend on aligning or comparing graduated scales through relative physical movement, rather than merely measuring an external length.
Scale spacing and labels encode mathematical relationships; establish whether apparent ruler markings are computational scales or only length graduations.
Distinguish a slide rule from a fixed logarithmic reference scale by identifying the movable scale or reading arrangement used to combine inputs.
Distinguish a slide rule from an electronic calculator by checking whether the result is read from physical scale alignment rather than electronically computed.
For a specialised calculating disc or gauge, establish whether its scale relationships and operating method place it within this registry entry.
Scope
+ Identification of linear, circular or other slide-rule configurations
+ Scale markings, mathematical relationships and supported calculations
+ Relative movement of scales and operation of cursors or other reading references
+ Legibility, alignment, mechanical condition and calculation checks
+ Instrument-specific handling, adjustment and readiness for use
- General mathematical theory and calculation instruction independent of the instrument
- Electronic calculators, software emulators and their implementation
- Ordinary measuring rulers and dimensional measurement of external objects
- The engineering system or professional decision in which a calculated result is used
- Ownership, market valuation and collection management beyond instrument identification
Characteristics
- Instrument configuration
- linear; circular; other documented configuration; unresolved Determines how scales move, how readings are transferred and which inspection method is appropriate.
- Scale inventory
- observed labels, faces, endpoints, graduation directions and documented mathematical functions Establishes which calculations the actual instrument supports without inferring capability from appearance alone.
- Usable scale extent
- millimetres along a linear scale or degrees of a circular scale, with the scale identified Helps assess reading separation and compare the physical extent available for interpolation.
- Relative-motion condition
- smooth and stable; binding; loose; slipping; seized; untested Determines whether settings can be made and retained reliably.
- Reading-reference arrangement
- cursor hairline; rotating pointer; fixed index; direct scale comparison; other observed arrangement Determines how values are aligned and transferred between scales.
- Scale and reference legibility
- readable; locally obscured; worn; ambiguous; unreadable, with affected positions recorded Identifies operations or ranges that cannot be read confidently.
- Alignment discrepancy
- millimetres, degrees or local graduation fractions at named reference positions Separates observable misalignment from uncertainty in visual interpolation.
- Demonstrated calculation deviation
- signed absolute or relative deviation for specified inputs, scales and reading conditions Supports a bounded judgment of computational usability rather than an unsupported accuracy rating.
- Magnitude and sign interpretation
- read directly for the operation; requires external reasoning; unresolved Prevents a scale reading from being mistaken for a complete numerical answer.
- Applicable operating documentation
- identified manual or scale explanation, with evidence that it matches this instrument Supports interpretation of unfamiliar scales, special marks and permitted adjustments.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 28 questions.
Instrument identity Establishes whether the object is a slide rule and identifies its particular configuration.
An agent must distinguish computational scale mechanisms from measuring rulers and related calculating aids before interpreting markings.
Computational identity
Examines the physical arrangement that makes the object a calculating instrument.
Relative scale calculation
Record evidence that scale alignment or relative movement combines numerical inputs.
- Which physical scales, indices or pointers move relative to one another to perform a calculation? definition
- What distinguishes this object from a measuring ruler, fixed reference scale or neighbouring type of calculating aid? boundary
Configuration and documentation
Connects the observed instrument to an identifiable layout and applicable instructions.
Layout identification
Record the configuration, identifying marks and evidence linking documentation to the actual scale layout.
- Is the instrument linear, circular or another configuration, and which faces carry computational scales? definition
- Which maker, model or other markings support identification, and what documentation matches the observed scales? provenance
Scale semantics Describes what the markings mean and which operations their relationships support.
Scale labels and arrangements determine computational capability; the presence of a slide alone does not establish it.
Scale functions
Interprets each computational scale and its reading conventions.
Graduation meaning
Record observed labels, numerical spans, directions and verified mathematical interpretations.
- What function, numerical interval and reading direction does each scale represent? definition
- What documentation or checked scale positions support the interpretation of unfamiliar labels and special marks? provenance
Operation coverage
Connects available scale combinations to usable operations and their restrictions.
Supported scale pairings
Record how particular scales and indices support an operation, including range and interpretation limits.
- Which scale pairings and index settings support each claimed operation on this instrument? action
- Where does an operation require a different index, another scale, or external determination of sign or order of magnitude? boundary
Setting and reading mechanism Assesses whether inputs can be positioned, retained and read consistently.
Computational use depends on controlled relative motion and dependable reading references.
Scale motion
Examines movement through the usable range and stability after setting.
Setting stability
Record binding, looseness, slipping and interference that affect scale positioning.
- Does the movable member travel through its intended range without binding or unintended disengagement? measurement
- Does a setting remain stable while the reading reference is moved and the instrument is handled normally? measurement
Reading references
Examines the indices, hairlines or pointers used to align and transfer readings.
Reference integrity
Record missing, displaced, obscured or ambiguous references and their effects on readings.
- Which references are required for the intended operations, and are they present and clearly readable? definition
- When a reference transfers a reading between scales, what discrepancy or viewing-angle sensitivity is observable? measurement
Computational confidence Bounds confidence in results using alignment checks, readable resolution and calculation trials.
A plausible-looking scale reading is insufficient evidence that an instrument is suitable for a particular calculation.
Alignment and resolution
Assesses agreement at reference positions and the ability to distinguish nearby values.
Local reading limits
Record alignment discrepancies and interpolation limits at identified scale positions.
- At documented reference settings, how closely do the expected marks agree across the usable scale range? measurement
- Which scale regions have graduation spacing, wear or obstruction that limits reliable interpolation? boundary
Calculation validation
Checks representative operations and separates observed performance from assumptions.
Verified use envelope
Record test inputs, scale choices, expected results, observed readings and the conditions under which use is justified.
- For known calculations covering the intended operations and scale regions, what deviations and repeated-reading variation are observed? measurement
- Given those checks and the required result tolerance, which calculations may proceed and which require another method? action
Condition and intervention Relates material and component condition to continued calculation, handling and adjustment.
Deformation, surface damage and unsuitable interventions can alter the scale relationships on which the instrument depends.
Calculation-affecting condition
Identifies physical defects that compromise scale geometry, movement or reading.
Functional damage
Record warping, cracks, detached markings, damaged moving members and other defects with their specific computational consequences.
- What visible deformation or damage affects scale alignment, movement or reading references? measurement
- Which defects prevent all use, and which restrict only particular scales, positions or operations? boundary
Permitted interventions
Determines suitable handling and adjustment from the actual construction and supporting instructions.
Care and adjustment basis
Record the evidence supporting cleaning, adjustment or component replacement and the checks required afterward.
- Which instructions establish suitable cleaning or adjustment methods for this instrument's materials, markings and mechanism? provenance
- What intervention is justified by the observed fault, and which alignment and calculation checks must follow it? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Straight simplex (scales on one face), including the Mannheim, Rietz and Darmstadt layouts
- Straight duplex (scales on both faces, typically with a wraparound or double-hairline cursor)
- Circular slide rules
- Cylindrical and helical rules (Fuller, Thacher, Otis King and similar long-scale instruments)
- Pocket rules (commonly about 5 inch / 12.5 cm scale length) versus desk 10-inch and 20-inch precision rules
- Log-log (LL) scientific rules versus basic student rules with few scales
- Application-specific rules (electrical, chemical, hydraulic, artillery, textile, commercial)
- Classroom demonstration rules (metre-scale teaching instruments)
- Which of these kinds and varieties hold for the sense of slide rule this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Library of Congress Subject Headings (LCSH) - Slide-rule - Established heading; hyphenated form is the authority string.
- Wikidata - item labelled 'slide rule' in English - Numeric Q-id not confirmed in this pass; do not treat a guessed Q-number as an identifier.
- Maker model number - Vendor-specific strings such as Keuffel & Esser 4080/4081-series, Pickett N-series, Faber-Castell 2/83N, Hemmi model numbers - These are the identifiers actually used in trade, catalogues and collections; there is no single global product code for the class.
- Which of these identifiers and schemes hold for the sense of slide rule this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- No current ISO or IEC product standard governs slide rules as manufactured calculating instruments; the class is obsolete for professional calculation.
- Scale arrangements used in manufacture were de facto conventions (Mannheim, Rietz, Darmstadt), not a single statutory code.
- National instrument standards historically existed in some manufacturing countries (notably JIS in Japan for 計算尺 and DIN practice in Germany for Rechenschieber); exact current designations were not verified in this pass and are not asserted by number.
- Which of these standards and regulation hold for the sense of slide rule this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Personal calculating instrument of engineers, scientists, surveyors, architects and military technical officers from the late nineteenth century until pocket electronic calculators displaced it in the early 1970s.
- Used for products, quotients, proportions, roots, powers, trigonometry and logarithms in design offices, field books and examination halls; the user supplied the decimal-point / power-of-ten separately.
- Aviation training still uses circular flight computers that are specialised circular slide rules (time-speed-distance and wind triangle).
- Now encountered mainly as antiques, museum objects, teaching props for logarithms and analog computation, and a specialist collectors' market.
- Which of these real-world use hold for the sense of slide rule this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Named scale length (D-scale, typical commercial sizes) - 12.5 (pocket 5-inch), 25 (standard 10-inch), 50 (20-inch precision) - cm
- Overall instrument length (straight rules) - about 15-30 for pocket and 10-inch models; about 50-55 for 20-inch - cm
- Working precision (significant figures readable on a 25 cm logarithmic D-scale) - about 3 (sometimes a guarded fourth) - significant figures
- Number of engraved scales - about 6-10 on a student simplex; 20-30 or more on a duplex log-log rule - count
- Mass (typical 10-inch wood, bamboo or plastic rule) - about 50-200 - g
- Which of these typical measurements hold for the sense of slide rule this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Order-of-magnitude error: the rule does not track powers of ten; a correct mantissa with a wrong decimal point is the characteristic user failure.
- Reading the wrong scale (A versus C/D, CI versus C, LL versus log) or misplacing the cursor hairline, including parallax.
- Dimensional instability: humidity warping of wood or bamboo; shrinkage, cracking or delamination of celluloid scale facings (a well-known failure of some mid-twentieth-century laminated rules).
- Slide too tight, too loose, or binding; worn or missing cursor; broken or displaced hairline.
- Limited precision (typically three significant figures) treated as if it were exact, then propagated into engineering or navigation results.
- The object itself is not a regulated hazard; harm comes from a trusted miscalculation, not from the instrument as a physical product.
- Which of these failure modes and hazards hold for the sense of slide rule this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- English names: slide rule (common), slide-rule (LCSH and some British hyphenation); older 'sliding rule'.
- German Rechenschieber; French règle à calcul; Japanese 計算尺 (keisanjaku); Russian логарифмическая линейка; Chinese 计算尺.
- Layout names travel internationally (Mannheim from France, Darmstadt from Germany) even when the spoken name of the object differs.
- Construction practice differed by maker region: Japanese Hemmi bamboo-core rules; United States mahogany or later plastic with celluloid facings (Keuffel & Esser) and aluminium bodies (Pickett); German Aristo, Nestler and Faber-Castell plastics.
- As a living calculating tool the instrument is globally obsolete; remaining named practice is strongest in aviation (circular flight computers) and in collector communities in Japan, Germany, the United Kingdom and the United States.
- Which of these regional variation hold for the sense of slide rule this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Ruler (measuring scale) - A ruler encodes length in a metrological unit; a slide rule's scales encode functions (chiefly logarithms). If aligning two marks computes a product rather than a length, it is a slide rule.
- Nomogram (alignment chart) - A nomogram is a fixed printed chart read with a straightedge; a slide rule has a moving scale (and usually a cursor). No sliding member means it is not a slide rule.
- Mechanical digital calculator (arithmometer, Curta, pinwheel machines) - Those machines perform discrete geared addition and related operations and display digits; a slide rule is analog, continuous, and read by interpolation on scales.
- Abacus - An abacus is a discrete place-value counting frame; a slide rule is a continuous logarithmic analog device.
- Aviation flight computer (E6B and similar) - It is a specialised circular slide rule for time-speed-distance and wind problems. Treat it as a neighbour when the registry sense is the general engineering slide rule: the test is presence of aviation-specific scales and (usually) circular form rather than a general C/D logarithmic pair as the primary interface.
- Sector (proportional compass) - A sector is a hinged pair of inscribed legs used with a pair of dividers; a slide rule uses coaxial sliding scales. Related historically, different mechanism.
- Printed logarithmic tables - Same mathematical method (addition of logarithms), different embodiment: look-up in a book versus mechanical scale alignment.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of slide rule this model covers, and on what evidence? provenance
Sources
- Slide rule. Wikipedia, Wikimedia Foundation. - Instrument definition, scale families (Mannheim, Rietz, Darmstadt, duplex, circular, cylindrical), typical sizes, historical use until electronic calculators, and common failure and reading issues.
- Cajori, Florian. A History of the Logarithmic Slide Rule and Allied Instruments. The Engineering News Publishing Company, New York, 1909. - Origin in logarithmic scales (Oughtred and successors), distinction from sectors and tables, and the early straight versus circular forms.
- Journal of the Oughtred Society. The Oughtred Society. - Collector and historian classification of makers, layouts, duplex versus simplex construction, Japanese bamboo-core practice, and celluloid-delamination and warping as known physical failures.
What the second pass must settle
- Where should this registry entry draw its boundary around specialised calculating discs, cylindrical instruments and other mechanisms using related scale principles?
- Which authoritative references explain scale-label variants and special marks without assuming that similarly labelled scales always have identical conventions?
- What representative calculation checks adequately cover each configuration and scale family?
- How should acceptable reading uncertainty be established for a particular instrument, operator and intended task?
- Which material-specific care and adjustment instructions are supported for the instrument being assessed?