A Letter from Dr. John Lining to C. Mortimer M. D. Sec. R. S. concerning the Weather in South-Carolina; With Abstracts of the Tables of His Meteorological Observations in Charles-Town

XII. A Letter from Dr. John Lining to C. Mortimer M.D. Sec. R.S. concerning the Weather in South-Carolina; with Abstracts of the Tables of his Meteorological Observations in Charles-Town. SIR, Read May 6. 1748. THO' I have not the Pleasure of a personal Acquaintance with you, yet as you are one of the Secretaries to the Royal Society, I take the Liberty to send you some Tables and Observations deduced from a Diary of the Weather, which I have kept for some Years past in this Town, which you may communicate to the Royal Society, if you think they will be acceptable. As an Account of the Instruments which I have used, and their Situation, is already published in the Philosophical Transactions*, I shall not trouble you with a Repetition of those Affairs. The Vicissitudes of the Weather, with respect to Heat and Cold, are perhaps no-where greater than in Carolina; and our Summer's Heat is probably not inferior to that under most Places of the Equator; nor is our Winter's Cold much less at some times than that in Britain. From near eight Years Observation, the greatest Increase of the Heat of the Air, which I have discover'd in 24 or 30 Hours, in Spring, Summer, Autumn, and Winter, was 19, 24, 13, and 16 Degrees * No. 470, p. 497-8. Degrees of Fahrenheit's Thermometer; and the greatest Decreases of Heat, in the same Spaces of Time, in those Seasons, were 35, 32, 27 and 27 Degrees respectively. It frequently happens, that one Day is ten or more Degrees warmer than the preceding Day; but the Decreases of Heat are always greater and more sudden than its Increases. On the 10th of January 1745, at 2 p.m., the Mercury in the Thermometer was at 70; next Morning it had sunk to the 26th Degree; and on the 12th Day in the Morning it was at 15, which was the greatest and most sudden Change I have seen. In Summer, the Heat of the shaded Air, about 2 or 3 in the Afternoon, is frequently between 90 and 95 Degrees; and on the 14th, 15th, and 16th of June 1738, at 3 p.m., it was 98; a Heat equal to the greatest Heat of the human Body in Health. In Winter I never but once saw the Thermometer so low as 15: Therefore the Difference between the most intense Heat and Cold of the shaded Air, in this Province, is 83 Degrees; which is a much greater Range than could well have been expected in this Latitude; and taking the Mean between those Extremes, 56 should be the temperate Degree of Heat in this Province: But the Sum of the thermometrical Altitudes, divided by the Number of Observations which I made for some Years together, gives 66, which may therefore more justly be reckoned the temperate Heat in Carolina, which exceeds 48, the temperate Heat in England, more than that exceeds the freezing Point. The mean Heat of the shaded Air, in Spring, Summer, Autumn, and Winter, taken from the mean nocturnal Heat, and from the mean Heat at 2 or 3 p.m. is 61, 78, 71, and 52 Degrees. The mean Heat of the shaded Air at 2 or 3 p.m. in Spring, Summer, Autumn, and Winter, is 65, 82, 75, 55 Degrees; and the mean nocturnal Heat in these Seasons is 57, 74, 68, and 49 Degrees. Therefore our Winter's nocturnal Heat, at a Medium, coincides nearly with the temperate Heat in England. The Thermometer, when suspended five Feet from the Ground, and exposed to the direct Rays of the Sun, and to those reflected from our sandy Streets, has frequently rose in a few Minutes, from 15 to 26 Degrees, above what was at that time the Heat of the shaded Air (but I have never yet made that Experiment when the Heat of the shaded Air was above 88): When we are therefore exposed in the Streets to the Sun in Summer, we inspire Air from 4 to 28 Degrees warmer than the Heat of the human Body. The Thermometer, when buried in the Sands of the Streets, when the Heat of the shaded Air was 88, rose in 5 Minutes to 108, tho' there was at the same time a moderate Wind. In June 1738, when the Heat of the shaded Air was 98, the Thermometer sunk one Degree in my Arm-pits; but continued at 98 in my Hand and Mouth: From which we see what little Concern the Air has in cooling the Blood in the Lungs. Two Men who were then in the Streets (when the Heat was probably 124 or 126 Degrees, as the shaded Air's Heat was then 98) dropp'd suddenly dead; and several Slaves in the Country, at Work in the Rice-Fields, shared the same Fate. I saw one of the Men immediately after he died; his Face, Neck, Breast, and Hands, were livid. From the barometrical Table it appears, that the Barometer's mean Altitude, taken from its greatest and least Height, is 30.09 Inches; and that its Range is only 1.22 Inch. Wherefore our Atmosphere varies only $\frac{1}{75}$ Part in its Weight. In the warm Months, the mean barometrical Station, taken from its greatest and least Altitudes in these Months, is 30.09 Inches; and I have never yet seen its Range in these Months exceed $\frac{58}{100}$ Parts of an Inch: Therefore the Changes of our Atmosphere's Weight, in the warm Months, will have but little Effect upon human Constitutions, as the Difference between its greatest and least Pressure is but $\frac{1}{7}$ Part of that in cold Climates, where the Range of the Barometer is three Inches. May not the great Height of the Barometer in the warm Months in this Climate, proceed from the vast Quantity of Water, which is at that time supported in our Atmosphere, as the Exhalation is then very great; or may it not proceed from the Rarefaction of the Mercury? For the Weight of the mercurial Column, at equal Altitudes, will be different under different Degrees of Heat; and the Mercury may therefore be supported at equal Heights by Columns of Air of unequal Weights. It appears, from the barometrical Table, that our Easterly or northerly Winds elevate the Mercury, and that our Southerly or Westerly Winds depress it; and I have as yet never observed the contrary. I beg you will be good enough to excuse this long Epistle, and believe that it comes from one who has a sincere Regard to the Improvement of Natural Knowledge, and one who is, SIR, Your most humble Servant, John Lining. A TABLE A Table of the highest and lowest Stations of Fahrenheit's Mercurial Thermometer in the shaded Air, with the mean meridian and nocturnal Heat, taken after Dr. Jurin's Method. | Year | Highest | Lowest | Mean Altitude | |------|---------|--------|---------------| | | | | about 10 p.m. | | | | | in the Heat of the Day | | 1738 | | | | | 1739 | | | | | 1740 | | | | | 1742 | | | | | Month | Highest | Lowest | Mean Altitude | |-------|---------|--------|---------------| | January | 71 | 69 | 67 | | February | 72 | 75 | 75 | | March | 74 | 79 | 80 | | April | 86 | 84 | 83 | | May | 91 | 86 | 87 | | June | 98 | 90 | 90 | | July | 91 | 89 | 91 | | August | 89 | 87 | 90 | | September | 83 | 88 | 84 | | October | 74 | 79 | 73 | | November | 70 | 69 | 67 | | December | 67 | 70 | 69 | The Means Y y 1739 | Month | Mean Altitude in the Heat of the Day | Mean Altitude about 10 P.m. | Mean Altitude about 10 P.m. in the Heat of the Day | |-----------|-------------------------------------|-----------------------------|---------------------------------------------------| | January | 49° 43' | 55° 49' | 6° 51' | | February | 59° 49' | 52° 45' | 8° 54' | | March | 63° 54' | 60° 53' | 6° 59' | | April | 74° 65' | 77° 67' | 8° 70' | | May | 78° 70' | 79° 70' | 7° 75' | | June | 83° 74' | 83° 72' | 10° 79' | | July | 86° 76' | 86° 79' | 8° 81' | | August | 81° 74' | 87° 75' | 8° 79' | | September | 78° 72' | 76° 69' | 5° 73' | | October | 63° 56' | 66° 58' | 8° 62' | | November | 56° 5c' | 53° 46' | 6° 53' | | December | 48° 41' | 57° 48' | 6° 51' | The Means: 68° 60' 69° 61' 69° 62' 7° 65½' A Table of the highest and lowest Barometrical Stations; with the Directions which the Wind then had. x A Northerly or Easterly Wind a A Southerly or Westerly Wind | Jan. | Feb. | March | April | May | June | July | Aug. | Sept. | Oct. | Nov. | Dec. | |------|------|-------|-------|-----|------|------|------|-------|------|------|------| | 30.48 N | 29.88 SW | .60 | 30.38 NE | 29.68 S | .70 | 30.26 SE | 29.58 S | .68 | 30.38 Wx | 29.78 WSW | .60 | | 30.42 E | 29.48 W | .94 | 30.38 E | 29.80 W | .55 | 30.30 E | 29.98 SW | .32 | 30.38 E | 30.00 SW | .38 | | 30.23 NE | 29.85 S | .38 | 30.35 E | 29.88 NW | .50 | 30.38 E | 29.88 NW | .50 | 30.45 E | 29.68 W | .77 | | 30.20 NE | 29.85 W | .35 | 30.30 E | 29.98 SW | .32 | 30.38 NE | 29.98 SW | .40 | 30.38 E | 29.88 NW | .50 | | 30.13 SSWx | 29.83 SW | .30 | 30.38 E | 29.88 NW | .50 | 30.38 E | 29.88 NW | .50 | 30.35 NE | 29.58 W | .77 | | 30.18 E | 29.88 SW | .30 | 30.38 E | 29.88 NW | .50 | 30.38 E | 29.88 NW | .50 | 30.35 NE | 29.58 W | .77 | | 30.33 NNE | 29.85 SE | .48 | 30.38 E | 29.88 NW | .50 | 30.38 E | 29.88 NW | .50 | 30.35 NE | 29.58 W | .77 | | 30.33 E | 29.83 WNW | .50 | 30.45 E | 29.68 W | .77 | 30.35 NE | 29.58 W | .77 | 30.58 N | 29.75 NNW | .83 | | Jan. | Feb. | March | April | May | June | July | Aug. | Sept. | Oct. | Nov. | Dec. | |------|------|-------|-------|-----|------|------|------|-------|------|------|------| | 30.70 N | 29.50 NW | 1.20 | 30.46 NNE | 29.76 W | .70 | 30.54 NNE | 29.72 WSW | .82 | 30.40 ENE | 29.60 W | .80 | | 30.55 N | 29.85 W | .70 | 30.54 NNE | 29.72 WSW | .82 | 30.40 ENE | 29.60 W | .80 | 30.48 E | 29.58 W | .90 | | 30.50 SE | 29.65 W | .85 | 30.39 SX | 29.90 SSW | .40 | 30.28 ESE | 29.90 NE | .38 | 30.22 W | 29.98 SW | .24 | | 30.32 E | 29.75 NE | .57 | 30.39 SX | 29.90 SSW | .40 | 30.28 ESE | 29.90 NE | .38 | 30.22 W | 29.98 SW | .24 | | 30.28 E | 29.85 S | .43 | 30.39 SX | 29.90 SSW | .40 | 30.28 ESE | 29.90 NE | .38 | 30.22 W | 29.98 SW | .24 | | 30.18 SX | 29.86 S | .32 | 30.28 ESE | 29.90 NE | .38 | 30.22 W | 29.98 SW | .24 | 30.25 NE | 29.95 N | .30 | | 30.08 SSEx | 29.85 SSW | .23 | 30.22 W | 29.98 SW | .24 | 30.25 NE | 29.95 N | .30 | 30.36 NE | 29.86 S | .50 | | 30.26 E | 29.85 W | .41 | 30.25 NE | 29.95 N | .30 | 30.36 NE | 29.86 S | .50 | 30.36 NE | 29.86 S | .50 | | 30.28 NE | 29.85 NE | .43 | 30.36 NE | 29.86 S | .50 | 30.36 NE | 29.86 S | .50 | 30.50 N | 29.95 W | .55 | | 30.32 NNE | 29.72 SW | .60 | 30.50 N | 29.95 W | .55 | 30.55 NW | 29.73 SW | .82 | 30.58 NNE | 29.65 WNW | .93 | | 30.51 N | 29.72 S | .79 | 30.55 NW | 29.73 SW | .82 | 30.58 NNE | 29.65 WNW | .93 | A Table of the Depth of Rain, in Inches and millesimal Parts, which fell in Charlestown. | | 1738 | 1739 | 1740 | 1741 | 1742 | |--------|------|------|------|------|------| | January| 1.097| 2.310| 4.873| 4.492| 2.189| | February| 4.416| 2.875| 3.084| 4.615| 1.650| | March| 4.532| 5.609| 1.141| 5.713| 5.203| | April| 1.082| 0.195| 1.092| 1.308| 0.918| | May| 3.127| 5.120| 5.612| 4.841| 5.898| | June| 1.567| 1.839| 4.648| 5.538| 3.250| | July| 1.660| 5.452| 3.013| 3.399| 1.252| | August| 4.104| 2.211| 7.301| 7.144| 7.647| | September| 1.792| 4.834| 3.200| 6.734| 2.895| | October| 1.358| 6.593| 1.258| 3.399| 0.759| | November| 2.656| 1.235| 1.848| 2.964| 3.388| | December| 3.877| 1.689| 2.736| 1.919| 0.957| | Total Depth| 149.268| 165.962| 139.806| 152.066| 136.006| | | 1743 | 1744 | 1745 | The Means | 1746 | |--------|------|------|------|-----------|------| | January| 3.172| 1.994| 0.863| 2.624| 1.144| | February| 2.435| 3.063| 7.739| 3.735| 2.701| | March| 0.621| 0.582| 3.229| 3.329| 1.628| | April| 5.292| 2.866| 3.842| 2.074| 1.128| | May| 2.535| 2.871| 1.832| 3.979| 3.988| | June| 1.903| 5.814| 9.510| 6.009| 4.109| | July| 7.738| 8.437| 6.771| 5.840| 9.895| | August| 3.767| 4.202| 9.339| 6.964| 6.114| | September| 4.686| 5.657| 0.754| 4.944| 0.932| | October| 1.672| 1.595| 2.962| 2.450| | | November| 3.220| 1.562| 0.682| 2.194| | | December| 2.706| 9.680| 2.623| 3.523| | | Total Depth| 39.747| 48.323| 50.146| 47.666| XIII.