John Harrison H4 Longitude History Lookup
Return a Royal Museums Greenwich fact about the 1714 Longitude Act, H4's completion, Barbados trial, 1765 payment dispute, or 1766 Royal Observatory test.
Description
Harrison’s H4 belongs to the history of marine longitude determination.
Harrison’s H4 belongs to the history of marine longitude determination. Its construction, sea trial and later reward dispute are separate historical events.1
Return a Royal Museums Greenwich fact about the 1714 Longitude Act, H4's completion, Barbados trial, 1765 payment dispute, or 1766 Royal Observatory test.
When to use John Harrison H4 Longitude History Lookup
Use this tool to return a Royal Museums Greenwich fact about the 1714 Longitude Act, H4's completion, Barbados trial, 1765 payment dispute, or 1766 Royal Observatory test.
Choose a supported reference focus or prepare the watch measurements, evidence and explicit limits requested. Confirm units and date conventions before running.
How to use John Harrison H4 Longitude History Lookup and understand its results
- Choose a supported reference focus or prepare the watch measurements, evidence and explicit limits requested. Confirm units and date conventions before running.
- Enter historyFocus using the field table and calculation rules, then run the tool.
- Read historyFocus, keyDate, verifiedStatement. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| historyFocus | John Harrison H4 history focus | string; one of "act", "completion", "barbadosTrial", "paymentDispute", "royalObservatoryTest" | Required |
Select an exact supported historyFocus value from the field table and run the lookup. The implementation selects a fixed local table entry and returns the fields shown below. Matching is case-sensitive, with no trimming, synonyms or free-text search. Any keyDate output can be a date, period or context label.
result=stored entry for selected focus Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| historyFocus | John Harrison H4 history focus | string |
| keyDate | Key date | string |
| verifiedStatement | Verified H4 history statement | string |
{
"input": {
"historyFocus": "completion"
},
"output": {
"historyFocus": "completion",
"keyDate": "1759",
"verifiedStatement": "Royal Museums Greenwich identifies H4 as John Harrison's prize-winning longitude watch, completed in 1759 after work began in 1755."
}
}Limitations and assumptions
No individual chronometer, trial record or archive document is authenticated. No sources are fetched or statements updated at runtime.
Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Marine Chronometer Gimbal Purpose Lookup: Return the bowl, ring-gimbal, box, handling, or lock-state function of a historical marine chronometer and its carrying case. For a complementary task, use Christiaan Huygens Pendulum History Lookup: Return a Smithsonian or APS-verified fact about Huygens's 1656 pendulum clock, 1657 patent, Galileo distinction, balance spring, or marine limitation.
References
Similar or alternative tools
- Marine Chronometer Gimbal Purpose Lookup
Return the bowl, ring-gimbal, box, handling, or lock-state function of a historical marine chronometer and its carrying case.
- Christiaan Huygens Pendulum History Lookup
Return a Smithsonian or APS-verified fact about Huygens's 1656 pendulum clock, 1657 patent, Galileo distinction, balance spring, or marine limitation.