Analysis of Weather Memorandum Book
1817. January. Having been stationary at home since Mar.1 1809. with opportunity and leisure to keep a meteorological diary, with a good degree of exactness, this has been done: and, extracting from it a term of seven years compleat, to wit from Jan. 1. 1810. to Dec. 31. 1816. I proceed to analyse it in the various ways, and to deduce the general results which are of principal effect in the estimate of climate. the observations (3905. in the whole) were taken before sunrise of every day; and again between2 3. and 4. aclock P.M. on some days of occasional absence, they were necessarily omitted. in these cases the averages are taken from the days of the same denomination in the other years only, and in such way as not sensibly to affect the average of the month, still less that of the year, and to be quite evanescent in their effect on the whole term3 of 7. years.
The table of thermometrical observations on the next page shews4 the particular temperature of the different seasons, and5 different years from 1810. to 1816. inclusive. it’s most interesting results however are that the range of temperature with us may be considered as within the limits of 5½.° and 94½°6 of Fahrenheit’s7 thermometer; and that 55½° is it’s mean and characteristic measure. these degrees fix the laws of the animal and vegetable races which may exist with us; and the comfort also of the human inhabitant, so far as depends on his sensations of heat and cold.8 still it must be kept in mind that this is but the temperature of Monticello; that in the Northern and Western parts of the state, the Mean and Extremes are probably something lower, and in the Southern and Eastern, higher. but this place is so nearly central to the whole state, that it may fairly be considered as the Mean of the whole.
|A Table of thermometrical observation made at Monticello from Jan. 1. 1810. to Dec. 31. 1816.|
It is a common opinion that the climates of the several states of our union have undergone a sensible change since the dates of their first settlements; that the degrees both of cold & heat are moderated. the same opinion prevails as to Europe: & facts gleaned from history give reason to believe that, since the time of Augustus Caesar, the climate of Italy, for example, has changed regularly at the rate of 1.° of Fahrenheit’s thermometer for every century. may we not hope that the methods invented in latter times for measuring with accuracy the degrees of heat and cold, and the observations which have been & will be made and preserved, will at length ascertain this curious fact in physical history?
Within the same period of time, about 50. morning observations, on an average, of every winter, were below the freezing point, and about 10. observations of the afternoon. this gives us 50. freezing nights,11 & 10. freezing days for the average of our winters.12
It is generally observed that when the thermometer is below 55.° we have need of fire in our apartments to be comfortable. in the course of these 7. years the number of observations below 55.° in each year were as follows.13
whence we conclude that we need constant fires four months in the year, and in the mornings and evenings a little more than a month preceding & following that term.16
|The 1st white frost in||1809.||10.||was Oct.||25.||the last||Apr.||11.|
but we have seen, in another period, a destructive white frost as early as September.
|Our first ice in||1809.||10.||was||Nov.||7.||the last||Apr.||10.|
The quantity of water (including that of snow) which fell in every month & year of the term was as follows.
from this table we observe that the average of the water which falls in a year is 47¼ I. the minimum 41½ and maximum 61.I. from tables kept by the late Colo James Madison, father of the President of the US. at his seat about miles N.E. from Monticello, from the year 1794. to 1801. inclusive, the average was 43¼ I. the minimum 35¾ I. and the maximum 52.I.
During the same 7. years there fell 622. rains, which gives 89. rains for every year, or 1. for every 4. days; and the average of the water falling in the year being 47¼ I. gives .53 cents of an inch for each rain, or .93 cents for a week, on an average, being nearly an inch a week.22 were this to fall regularly, or nearly so, thro’ the summer season, it would render our agriculture most prosperous, as experience has sometimes proved.
Of the 3905 observations made in the course of the 7. years 2776. were fair; by which I mean that the greater23 part of the sky was unclouded. this shews our proportion of fair to cloudy weather to be as 2776 : 1129 :: or as 5. to 2. equivalent to 5. fair days to the week. of the other 2. one may be more than half clouded, the other wholly so. we have then 5. of what astronomers call ‘observing days’ in the week; and of course a chance of 5. to 2. of observing any astronomical phaenomenon which is to happen at any fixed point of time.
|The snows24 at Monticello amounted to the depth|
|in||1809.||10||of||16¼||I. and covered the ground||19.||days.|
which gives an average of 22½ I. a year, covering the ground 22. days, and a minimum of 11.I. and 11. days, & maximum of 35.I. and 39. days. according to mr Madison’s tables, the average of snow, at his seat, in the winters from 1793.4. to 1801.2. inclusive, was 23½. the minimum 10⅛ & maximum 38½28 I. but I once (in 1772.) saw a snow here 3.f. deep.
The course of the wind having been one of the circumstances regularly observed. I have thought it better, from the observations of the 7. years, to deduce an average for a single year, & for every month of the year. this Table accordingly exhibits the number of days in the year, & in every month of it, during which each particular wind, according to these observations, may be expected to prevail. it will be for Physicians to observe the coincidences of the diseases of each season, with the particular winds then prevalent, the quantities of heat, rain Etc.
In this separate table I state the relation which each particular wind appeared to have with rain or snow. for example, of every 5. North winds, 1. was either accompanied with rain or snow, or followed by it before the next observation, and 4. were dry. of every 4. North Easters, 1. was wet, 3. dry Etc. the table consequently shews the degree in which any particular wind enters as an element into the generation of rain, in combination with the temperature of the air, state of the clouds Etc.
|at Monticello.33||at Montpelier.34|
|the Red maple comes into blossom from||Feb.||18.||to||Mar.||27.|
|the tick appears||15.||2.|
|the House Martin||18.||9.||21.||2|
|Asparagus comes first35 to table||23.||14.||31.||24|
|the Shad arrives||28.||18.|
|the Lilac blossoms||Apr.||1.||28.|
|the Whip-poor-will is heard||2.||21.||Apr.||12.||Apr.||24.|
|the Dogwood blossoms||3.||22.36|
|the Wood-Robin is heard||20.||to||May||1.|
|the Locust blooms||25.||17.|
|the 1st brood of houseflies||28||4||May||15.||May||18.37|
|the red clover first blossoms||May||1.||to|
|the garden-pea first at table||3.||25.||13.||29|
|strawberries first ripe||3.||25.||6.||28|
|Cherries first ripe||18.||25.||10||31|
|Artichokes first at table||28||to||June||12|
|Wheat harvest begins||June||21.||29||June||12.||July||6.|
|Cucumbers first at table||22.||to||July||5||14.||1.|
|Indian corn first at table||July||4.||July||16.||30|
|peaches first ripe||7.||21.||9||28.|
|the Sawyer first heard||14.||20||15||20.|
The natural season of the vegetable is here noted, & not the artificial one produced by glasses, hotbeds Etc. which combining art with nature, would not be a test of the latter separately.
Another Index of climate may be sought in the temperature of the waters issuing from fountains. if the deepest of the38 reservoirs feeding these may be supposed at like distances from the surface in every part of the globe, then the lowest39 temperature of water flowing from them would indicate that of the earth from and through which it flows. this will probably be found highest under the equator, and lower as you recede towards either pole.40 on an examination of 15. springs in the body of the hill of Monticello, the water of the coolest was at 54½°41 the outer air being then at 75.°42 a friend assures me that in an open well of 28. feet depth in Maine, Lat. 44°–22′ and in the month of August, the water in it being then 4.f. deep, it’s temperature was 52.° of Fahrenheit’s43 thermometer, that of the water of Kennebec river being at the same time 72½°
Lastly to close the items which designate climate, the latitude of Monticello is to be added, which, by numerous observations, lately made, with a Borda’s circle of 5.I. radius with Nonius divisions to 1.′ I have found, by averaging the whole, to be 37°–57′–51″–26.″′44
MS (DLC: Rives Papers, Miscellany); two sheets in TJ’s hand folded to form eight pages and stitched together into a booklet; partially dated; with note at head of text in an unidentified hand: “Mr. Jefferson’s Memoranda of Climate.” Dft (MHi); in TJ’s Weather Memorandum Book, 1802–16; incomplete and differently sequenced, with much of the commentary lacking; undated; with only the most significant variations noted below. Printed in Virginia Literary Museum and Journal of Belles Lettres, Arts, &c. 1 (1829): 26–9. Enclosed in TJ to James Madison, 22 June 1817.
During his five years of intermittent residence in Williamsburg as a member of the House of Burgesses, 1772–77, TJ began recording weather data. His first recorded purchase of a thermometer was in 1769, and he bought another one on 4 July 1776. The earliest extant portions of TJ’s meteorological diaries are held by DLC (1776–1820), with later observations in MHi (1802–16). In a summary of his early readings printed in his Notes on the State of Virginia, TJ noticed a change in climate and its attendant impact on humans and nature. He regarded documenting climatic change as one very practical reason to quantify weather data. While TJ did not engage directly with theories on the environmental causes of illness, he alluded above to the potential utility of wind studies for explaining the transmission of disease (MB description begins James A. Bear Jr. and Lucia C. Stanton, eds., Jefferson’s Memorandum Books: Accounts, with Legal Records and Miscellany, 1767–1826, 1997, The Papers of Thomas Jefferson, Second Series description ends , 1:29, 420, 432–6, 771–806; Notes, ed., Peden, 73–81; Silvio Bedini, Jefferson and Science , 29–34; James Rodger Fleming, Meteorology in America, 1800–1870 , 9–13).
In 1784 TJ prevailed upon future United States president James Madison to “keep a diary” that would include daily barometric and thermometric readings along with wind direction and such observations of the natural world as the emergence of plants and migrations of animals. TJ assured him that “It will be an amusement to you and may become useful.” Madison, possibly one or more of his brothers, and their father, the late colo james madison, dutifully kept a record of their readings for years. Over time TJ also received weather information from other observers, including his son-in-law Thomas Mann Randolph at Monticello in TJ’s absences, Bishop James Madison in Williamsburg, David Rittenhouse in Philadelphia, and John Breck Treat in Arkansas, Louisiana Territory (PTJ description begins Julian P. Boyd, Charles T. Cullen, John Catanzariti, Barbara B. Oberg, and others, eds., The Papers of Thomas Jefferson, 1950– , 40 vols. description ends , 6:507, 7:30–1, 231, 16:351–2, 20:327–30, 30:78–81; Madison, Papers, Congress. Ser., 8:514–5, 9:420–4; Treat to TJ, 31 Mar. 1809; TJ to Madison, 22 June 1817).
TJ provided a similar but more impressionistic discussion of meteorological readings he had kept in Washington during his presidency in a letter to Nathaniel Chapman, 11 Dec. 1809. He drew heavily on the analysis printed above in his 11 Apr. 1818 letter to Jacob Bigelow.
1. Word not in Virginia Literary Museum.
2. Reworked from “before.”
3. Virginia Literary Museum: “tenor.”
4. Dft begins here, with “this table shews.”
5. Preceding three words not in Virginia Literary Museum.
6. Virginia Literary Museum: “94°.”
7. Manuscript: “Farenheit’s.”
8. In Dft TJ here canceled “with the ordinary serenity of sky.”
9. Here and through this entire column in MS, TJ mistakenly flipped the “max.” and “min.” readings. Virginia Literary Museum followed the MS. The headings are editorially corrected above based on the Dft.
10. Instead of preceding two words, Virginia Literary Museum reads “clear weather.”
11. Preceding thirteen words not in Virginia Literary Museum.
12. Dft presents data from preceding paragraph in tabular form.
13. Paragraph not in Dft.
14. Manuscript: “12.” Virginia Literary Museum and Dft: “11.”
15. To the right of this table in Dft, TJ canceled a table tallying “clear or cloudy” days for the same date range and giving a total of 1,234 cloudy days out of 4,027 total observations. Dft ends here.
16. Virginia Literary Museum: “time.”
17. Preceding two tables included in variant form in Dft.
18. Virginia Literary Museum: “3.656.”
19. Virginia Literary Museum: “2.025.”
20. Virginia Literary Museum: “6.658.”
21. Thus in text, but only the final figure in the row is an average; those preceding it are totals for each given year.
22. Preceding nine words not in Virginia Literary Museum.
23. Virginia Literary Museum: “quarter.”
24. Dft resumes here.
25. In place of numeral, Virginia Literary Museum substitutes a blank space.
26. Virginia Literary Museum: “19.”
27. Dft ends here.
28. Virginia Literary Museum: “33½.”
29. Virginia Literary Museum: “5.”
30. Dft resumes here.
31. Word interlined in Dft in place of “Phaenomena.”
32. Instead of preceding three words, Dft reads “the earliest & latest days of their 1st appearance.”
33. Column heading supplied from Dft.
34. Heading, all data in this column, and vertical rules supplied from Dft.
35. Here and in many subsequent entries, TJ interlines “first” in Dft.
36. Entry interlined in Dft.
37. Entry supplied from Dft.
38. Preceding three words interlined in Dft.
39. Word interlined in Dft.
40. In Dft TJ here canceled “here I found from.”
41. In Dft TJ here canceled “but the others varying from that to 66° we may suppose their reservoirs to vary in depth also.”
42. Dft ends here.
43. Manuscript: “Farenheit’s.”
44. Final number not in Virginia Literary Museum.
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