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.

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

but we have seen, in another period, a destructive white frost as early as September.

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.

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.

An30 estimate of climate may be otherwise made from the advance of the spring, as manifested by animal and vegetable subjects.31 their first appearance32 has been observed as follows.

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