Object research · John Constable · The Courtauld · P.1952.RW.69
Cloud Study
21 September 1822, three o'clock · Hampstead campaign
“Sepr.21.1822. Looking South, brisk wind to east, warm and fresh. 3 o’cl. afternoon”
Courtauld catalogue transcription of the inscription on the verso. C1 Each phrase is underlined in its verdict and links to its row.
Finding · Nephos analysis · version 2026-09-07
Constable’s two notes, about ninety minutes apart, agree on the date, southward view, easterly wind and warmth. Because both notes are his, the match is internal consistency, not confirmation from another observer. Regional wind records fit an easterly day, but the picture cannot test the hour or view, and the temperature sources cannot decide what “warm” meant at his position.
The Nephos method
How this study was read
The method in fullWhat is written
21 September 1822, 3 o’cl. afternoon.
Sepr.21.1822. Looking South, brisk wind to east, warm and fresh. 3 o’cl. afternoon
Courtauld Gallery, P.1952.RW.69, as the museum transcribes it
Records of those days
- Luke Howard’s registerPrinted daily wind, thermometer and notes, The Climate of London. Kept at Tottenham or Stratford, not Hampstead.
- Central England TemperatureA regional daily mean for the Midlands, not a Hampstead reading.
- The computed sunPosition of the sun for the written hour at the assumed place.
Each claim tested
- “Sepr.21.1822.” A second inscription by Constable gives the same date.
- “3 o’cl. afternoon” The computed Sun at 15:00 is consistent with the afternoon, but a horizonless pure sky supplies nothing against which to test the stated time.
- “Looking South,” The computed sun would lie to the right of a south-facing painter, but no painted bearing can be measured from this view.
- “brisk wind to east,” Yale also says East; Howard records NE; the regional model reconstructs ENE at about 6.0 m/s.
- “warm and fresh.” The day sat inside a mild spell that fell sharply by the 26th, yet its 11.6°C daily mean was slightly below the prior 50-year average for 21 September, about 12.6°C.
- “Same-day consistency” The two inscriptions from the same hand agree on date, southward view, east wind and warmth.
Verdict
Constable’s two notes, about ninety minutes apart, agree on the date, southward view, easterly wind and warmth.
- Partially agrees“brisk wind to east,”, “Same-day consistency”
- Unknown“Sepr.21.1822.”, “3 o’cl. afternoon”, “Looking South,”, “warm and fresh.”
01 · The evidence
Six claims, four witnesses, one verdict each.
Each phrase of the inscription is a claim. Each column is a witness with its own place, scale and limit. A dash means that witness has nothing to say about that claim.
| Claim | Howard’s registerPrinted table · London area · C3 | Weather reconstructionRegional cell · C4 | The sunComputed · Hampstead assumed · C7 | Yale sheetSame hand · 13:30 · C6 | Verdict · Nephos |
|---|---|---|---|---|---|
| “Sepr.21.1822.” Unknown | Row 21The table has a row for the 21st. Nothing in it names a painter. | — | — | “Sep[br] 21. 1822.”A second inscription by Constable gives the same date. | A second inscription by Constable gives the same date. This is internal consistency between two notes from the same hand, not confirmation from a separate observer. C1 C6 Link to claim · Suggest a correction |
| “3 o’cl. afternoon” Unknown | —Day-level entries; no hour recorded. | 15:00 UTCStored model sample. | 25.9° alt · 234.1° azAt approximately 15:00 local mean time. | ½ past oneAbout ninety minutes earlier. | The computed Sun at 15:00 is consistent with the afternoon, but a horizonless pure sky supplies nothing against which to test the stated time. C7 Link to claim · Suggest a correction |
| “Looking South,” Unknown | — | — | SW, to the rightNo horizon or landmark fixes the painted bearing. | “looking south.” | The computed sun would lie to the right of a south-facing painter, but no painted bearing can be measured from this view. C7 Link to claim · Suggest a correction |
| “brisk wind to east,” Partially agrees | NEDay-21 cell, another London location. | ENE, 54° · 6.0 m/s15:00 UTC, cell about 111 × 68 km. | — | “wind very fresh at East,” | Yale also says East; Howard records NE; the regional model reconstructs ENE at about 6.0 m/s. The easterly sector is consistent across all three, but locations and direction labels differ. C3 C4 C6 Link to claim · Suggest a correction |
| “warm and fresh.” Unknown | Day maximum and minimumFirst thermometer at Howard’s station. | 13.9°CGrid-cell air temperature at 15:00. | — | “but warm.” | The day sat inside a mild spell that fell sharply by the 26th, yet its 11.6°C daily mean was slightly below the prior 50-year average for 21 September, about 12.6°C. No source defines “warm” or “fresh,” and none measures Constable’s position. C4 C5 Link to claim · Suggest a correction |
| Same-day consistency Partially agrees | NE · “Fine.” | Easterly, mild | Lower at threeFrom the Yale time to three o’clock. | Same date, view, wind, warmth | The two inscriptions from the same hand agree on date, southward view, east wind and warmth. The regional wind records are compatible with the easterly claim; the warmth claim remains unknown. No visual cloud comparison is claimed. C1 C3 C4 C5 C6 Link to claim · Suggest a correction |
Described. Constable’s “brisk wind to east” and “warm and fresh,” and Howard’s “Fine,” are words used by people in different contexts. Strength and felt warmth have no shared numerical scale.
Measured. Howard’s wind and thermometer and the Central England daily mean are instrumental records with their own locations and time coverage.
Estimated. The regional weather reconstruction and computed sun are calculations with stated assumptions. They do not turn painted cloud forms into a weather observation.
What is known and what cannot be known: the object identity and inscription are secure, and the regional records support a broadly easterly afternoon. They do not prove an exact painted bearing, gust strength, temperature adjective or hour from cloud forms alone.
02 · The witnesses
Four records of the afternoon, none of them the painting.
The values behind the table, each in its own units and with its own reach. No capture-to-capture cloud measurement has been performed.
Same-day object · C6
Two notes, one moving sky
Yale’s catalogue transcribes the inscription, which is on a label fixed to the stretcher: “Sep[br] 21. 1822. | ½ p’s[t] one o clock. | looking south. | wind very fresh at East, but warm.” This Courtauld sheet says three o’clock, looking south, with a brisk east wind, “warm and fresh.” C1 C6
13:30 Yale
15:00 Courtauld
E / E, both inscribed easterly. The notes agree on date, view, easterly wind and warmth. That is internal consistency between two inscriptions from the same hand, not proof from another observer.
The sun, computed · C7
The sun at three
25.9° altitude
234.1° azimuth
At approximately 15:00 local mean time over Hampstead, 51.56° N, 0.165° W. JPL Horizons / DE441; 15:01 UT approximates 15:00 local mean time.
For a painter looking south the sun was to the right, lower than during Yale’s earlier session. With no horizon, this cannot test a painted bearing.
Weather reconstruction · C4
The model at 15:00
ENE, from 54°
6.0 m/s over the London-area grid cell, about 111 × 68 km.
63% cloud
±34 points of ensemble spread; 13.9°C grid-cell air temperature at 15:00.
Regional context, not one Hampstead hilltop. The reconstruction used no painting.
Period register · C3
Howard’s day reading
NE wind
Howard’s London-area register for 21 September; “Fine.” covers the 17th through the 21st.
11.6°C daily mean
Central England. Prior 50-year average for the date about 12.6°C; the mild spell fell to 9.5°C by the 26th.
Howard’s northeast and the model’s east-northeast sit beside both inscriptions’ east, but adjacent compass sectors are not identical readings.
03 · Making the artwork
The sky passed through an artist’s decisions.
Production uncertainty is separate from weather uncertainty. The located sources do not establish every stage of this object’s making, and “unknown” is not evidence that a stage did not happen.
- Locationpartly known
- Hampstead supplies the campaign context; the exact easel location is not established in this record. C1 Affects view direction and solar comparisons.
- Date evidencesecurely dated inscription
- The date is carried through a museum catalogue transcription, not an independently timed observation of execution. C1 · Affected claim
- Outdoor executionunresolved
- The evidence assembled here does not establish that every passage was executed outdoors in the stated interval. Affects whether the inscription claims can be tested against depicted light or cloud forms.
- Preparatory work and later changesunknown
- No object-specific sequence of preparatory sketches or subsequent working sessions is established in this record. Unknown is not evidence that there were none. Affects any inference from painted form to a momentary sky.
04 · Revisions
How the reading changed.
Source verification and a change of conclusion are different events. Both are kept.
- Original claim
- Constable's Yale note at about 13:30 and Courtauld note at 15:00 give the same date, a southward view, an easterly wind, and warmth.
- Conflicting evidence
- Both notes are by Constable, so their agreement is internal consistency rather than evidence from another observer. Howard records NE and the regional model gives ENE rather than E; the shared date, view, and warmth remain unverified by the comparison, and no visual cloud comparison was performed.
- Conclusion now
- Partially agrees The same-day pair is treated as internal consistency within one artist's notes plus partial agreement with external wind evidence.
- Retained versions
- Yale Nephos record Courtauld object record Verified Nephos machine record Howard September 1822 page image
- What changed
- A first redesign brought the findings forward, compared the sources in their own words and stated the limits of what is known about how the study was made. This layout now places all claims and witnesses in one table. No new weather observation or independent validation was added. Read the page before the redesign. Its date names the saved copy; the original editing time was not recorded.
05 · Take this into your work
A record you can cite, print or embed.
Cite individual claims by their link, and cite museum and historical sources directly when using their statements. Nephos analysis is independent of the holding institution; image licences are separate from the research text. Inscription as transcribed by the Courtauld: “Sepr.21.1822. Looking South, brisk wind to east, warm and fresh. 3 o’cl. afternoon”
Machine-readable
For the Courtauld Gallery: this record is for P.1952.RW.69. If it is right, link it from your object page; if anything is wrong, write to Nephos and it will be corrected the same day.
The museum’s catalogue remains the authority. Nephos does not claim endorsement.
06 · Sources
Follow every claim.
- C1Courtauld Gallery: John Constable, Cloud Study, P.1952.RW.69; metadata, inscription and object record.https://gallerycollections.courtauld.ac.uk/object-p-1952-rw-69
- C2Courtauld IIIF manifest: image source, attribution statement and CC BY-NC 4.0 licence.https://gallerycollections.courtauld.ac.uk/api/iiif/O2918/manifest.json
- C3Luke Howard, The Climate of London, 2nd ed., vol. III, Table CXCVI, p. 90: 21 September wind and notes.https://archive.org/download/in.ernet.dli.2015.48048/page/n96.jpg
- C4Nephos verified Yale receipt: source-exact 20CRv3 arrays for 21 September 1822, including the 15:00 values used here.https://nephos-mocha.vercel.app/data/constable-analysis.json
- C5Met Office Hadley Centre: Central England Temperature daily means and prior 50-year calendar-date average.https://www.metoffice.gov.uk/hadobs/hadcet/data/meantemp_daily_totals.txt
- C6Yale Center for British Art: the distinct same-day Cloud Study, B1981.25.116; object record and current Yale LIDO inscription record.https://collections.britishart.yale.edu/catalog/tms:627
- C7NASA/JPL Horizons observer table: Sun over Hampstead, 21 September 1822, 13:01 to 15:01 UT.NASA/JPL Horizons query
- C8Courtauld Gallery copyright policy: non-commercial web use and required image credit.https://courtauld.ac.uk/gallery/copyright/