Daily Record, 1 November 1802-29 June 1826

Massachusetts Historical Society: Coolidge Collection of Thomas Jefferson Manuscripts, 1705-1827, Other Volumes, 1766-1824, Weather Recordings, 1782-1826.

84 pp. of daily weather observation records bound with 82 pp. of notes, tables, and memoranda on weather, climate, astronomical calculations, and other subjects.

Jefferson apparently began this record with the intention of recording only limited information, as the first page has the heading “Washington. Notes of the season,” followed by observations in notation form for 1 November–13 December 1802; he then changed to a columnar format, repeating information about those dates and continuing forward through 31 December 1816; the record then breaks off, resumes on a new page with 14 August 1825, and continues through 29 June 1826. Column headings in 1802–1803 identify observation times as sunrise and 3:00 PM; column headings in June 1805: “therm,” “I.” (for wind force), and “weather”; March 1806: “ther.” and “weather”; November 1806: “th. | wind | weather | Hygr”; November 1810: “Ther. | wind | weather”; January–April, July–August 1812: “Therm. | wind”; January–February 1816: “therm | wind | weather.” Check marks in pencil at the foots of columns on some pages perhaps relate to compilations of data by Jefferson.

From 16 December 1802 to 1 January 1804, the record includes temperature readings from a thermometer kept in an unheated bedroom, with notations of the position of the window each night; these readings have been separately transcribed as Bedroom Temperatures, 1802–1804.

Beginning at 25 November 1805, Jefferson put “+” or “-” next to some entries without explanation.

A note by Jefferson on temperature readings in his wine cellar and icehouse has been separately transcribed as Note on Temperatures in Wine Vault and Icehouse at Monticello, 11 June 1806.

At Monticello in the period from 12 to 21 April 1807, Jefferson made changes to most of his notations of wind direction, and in the majority of cases he made two changes to each reading. The morning notation of 13 April, for example, he first wrote as “SW”; he came back to strike through that and write “SE” in space he found in another column; then he came back again to write over the “SE” and make “NW” his final notation. In each case in which the cancellations are legible, he followed the same pattern, first changing the direction 90 degrees to the left, then changing that by 180 degrees to yield a net change of 90 degrees to the right of the original direction. That sequence of changes implies that there was a problem with equipment. Jefferson had arrived at Monticello on 11 April from Washington. His series of corrections to wind directions in his record for the days soon after his arrival may indicate that there initially was a problem in the installation of the arrow on the compass rose inside the house to show the direction indicated by the wind vane on the roof. The correction should have been 90 degrees to the right, that is S.W. to N.W. in the example above, but Jefferson made the change 90 degrees to the left and had to fix it a second time for each of the readings. The problem appears to have been resolved by 22 April.

On a page between pages with entries for April and May 1809, Jefferson made a table of snowfall of the previous seven winters; transcribed as Recapitulation of Depth of Snows, 1802–1803 to 1808–1809.

In margins of the record in 1809 and 1810, Jefferson made notes about the basis for his calculation of rainfall on the ground from the quantities measured in his rain gauge and about the relationship between readings of a rain gauge and a snow gauge; transcribed as Explanation of Rain Gauge, Summer 1809 and Additional Notes on Rain and Snow Gauges, Winter 1810.

On pages in the record at December 1809 and June 1810, Jefferson totaled the monthly amounts of rainfall for the last six months of 1809 and first six months of 1810; transcribed as Rainfall, July 1809–June 1810.

On the page of the record with entries for January and February 1811, Jefferson made calculations to convert quantities of snowfall to inches of rain; transcribed as Calculations of Precipitation, January–March 1811.

In November–December 1816 at Poplar Forest, Jefferson made his temperature readings using a Reaumur thermometer. Those readings have been converted to Fahrenheit temperatures for inclusion in the temperature data field.