AN ACCOUNT OF THE CLIMATE OF PENNSYLVANIA, AND ITS INFLUENCE UPON THE HUMAN BODY.
IN order to render the observations upon the epide|mic diseases which compose a part of this volume more useful, it will be necessary to prefix to them a short account of the climate of Pennsylvania, and its influence upon the human body. This account may perhaps serve further, to lead to future discoveries, and more extensive observations, upon this subject.
THE state of Pennsylvania lies between 39° 43′ 25″, and 42° north latitude, including, of course, 2° 16′ 35″, equal to 157 miles from its southern to its northern boundary. The western extremity of the state is in the longitude of 5° 23′ 40″, and the eastern, in that of 27′ from the meridian of Philadelphia, com|prehending in a due west course 311 miles, exclusive of the territory lately purchased by Pennsylvania from the United States, of which as yet no accurate surveys have been obtained. The state is bounded on the Page 58 south by part of the state of Delaware, by the whole state of Maryland, and by Virginia to her western ex|tremity. The last named state, the territory lately ceded to Connecticut, and Lake Erie, (part of which is in|cluded in Pennsylvania) form the western and north|western boundaries of the state. Part of New-York and the territory lately ceded to Pennsylvania, with a part of Lake Erie, compose the northern, and another part of New-York, with a large extent of New-Jersey (separated from Pennsylvania by the river Delaware) compose the eastern boundaries of the state. The lands which form these boundaries (except a part of the states of Delaware, Maryland, and New-Jersey) are in a state of nature. A large tract of the western and north-eastern parts of Pennsylvania are nearly in the same uncultivated situation.
THE state of Pennsylvania is intersected and diver|sified with numerous rivers, and mountains. To de|scribe, or even to name them all, would far exceed the limits I have proposed to this account of our climate. It will be sufficient only to remark, that one of these rivers, viz. the Susquehannah, begins at the northern boundary of the state twelve miles from the river De|laware, and winding several hundred miles through a variegated country, enters the state of Maryland on the southern line, fifty-eight miles westward of Philadel|phia; that each of these rivers is supplied by numerous streams of various sizes; that tides flow in parts of two of them, viz. in the Delaware and Schuylkill; that the rest rise and fall alternately in wet and dry weather; and that they descend with great rapidity, over prominent beds of rocks in many places, until they empty themselves into the bays of Delaware and Page 59 Chesapeak on the east, and into the Ohio on the west|ern parts of the state.
THE mountains form a considerable part of the state of Pennsylvania. Many of them appear to be reserved as perpetual marks of the original empire of nature in this country. The Allegany, which crosses the state about two hundred miles from Philadelphia, in a north inclining to an east course, is the most considerable and extensive of these mountains. It is called by the In|dians the backbone of the continent. Its height in dif|ferent places is supposed to be about 1300 feet from the adjacent plains.*
THE soil of Pennsylvania is diversified by its vici|nity to mountains and rivers. The vallies and bot|toms consist of a black mould, which extends from a foot to four feet in depth. But in general a deep clay forms the surface of the earth. Immense beds of lime|stone lie beneath this clay in many parts of the state. This account of the soil of Pennsylvania is confined wholly to the lands on the east side of the Allegany mountain. The soil on the west side of this mountain shall be described in another place.
THE city of Philadelphia lies in the latitude of 39° 57′, in longitude 75° 8′ from Greenwich, and fifty-five miles west from the Atlantic ocean.
IT is situated about four miles due north from the conflux of the rivers Delaware and Schuylkill. The buildings, which consist chiefly of brick, extend near|ly Page 60 three miles north and south along the Delaware, and above half a mile due west towards the Schuylkill, to which river the limits of the city extend; the whole including a distance of two miles from the Delaware. The land near the rivers, between the city and the con|flux of the rivers, is in general low, moist, and sub|ject to be overflowed. The greatest part of it is mea|dow ground. The land to the northward and west|ward, in the vicinity of the city, is high, and in ge|neral well cultivated. Before the year 1778 the ground between the present improvements of the city, and the river Schuylkill, was covered with woods. These, together with large tracts of wood to the northward of the city, were cut down during the winter the British army had possession of Philadelphia. I shall hereafter mention the influence which the cutting down of these woods, and the subsequent cultivation of the grounds in the neighbourhood of the city, have had upon the health of its inhabitants.
THE mean height of the ground on which the city stands, is about forty feet above the river Delaware. One of the longest and most populous streets in the city, rises only a few feet above the river. The air at the north is much purer than at the south end of the city; hence the lamps exhibit a fainter flame in its southern than its northern parts.
THE tide of the Delaware seldom rises more than six feet. It flows four miles in an hour. Its width near the city is about a mile.
THE city, with the adjoining districts of South-wark and the Northern Liberties, contain between 40 and 50,000 inhabitants.
Page 61 FROM the accounts which have been handed down to us by our ancestors, there is reason to believe that the climate of Pennsylvania has undergone a material change. Thunder and lightning are less frequent, and the cold of our winters and heat of our summers are less uniform, than they were forty or fifty years ago. Nor is this all. The springs are much colder, and the autumns more temperate than formerly, insomuch that cattle are not housed so soon by one month as they were in former years. Within the last eight years, there have been some exceptions to part of these ob|servations. The winter of the year 1779, 80, was uniformly and uncommonly cold. The river Dela|ware was frozen near three months during this winter, and public roads for waggons and sleighs connected the city of Philadelphia in many places with the Jer|sey shore. The thickness of the ice in the river near the city, was from sixteen to nineteen inches, and the depth of the frost in the ground was from four to five feet, according to the exposure of the ground and the quality of the soil. This extraordinary depth of the frost in the earth, compared with its depth in more northern and colder countries, is occasioned by the long delay of snow, which leaves the earth without a covering during the last autumnal and the first winter months. Many plants were destroyed by the intense|ness of the cold during this winter. The ears of horn|ed cattle and the feet of hogs exposed to the air, were frost-bitten; squirrels perished in their holes, and par|tridges were often found dead in the neighbourhood of farm-houses. The mercury in January stood for several hours at 5° below 0, in Farenheit's thermo|meter; and during the whole of this month, (except on one day) it never rose in the city of Philadelphia to the freezing point.
Page 62 THE cold in the winter of the year 1783, 4, was as intense but not so steady, as it was in the winter that has been described. It differed from it materially in one particular, viz. there was a thaw in the month of January which opened all our rivers for a few days.
THE summer which succeeded the winter of 1779, 80, was uniformly warm. The mercury in the ther|mometer, during this summer, stood on one day (the 15th of August) at 95°, and fluctuated between 93° and 80° for many weeks. The thermometer, in every reference that has been, or shall be made to it, stood in the shade in the open air.
I KNOW it has been said by many old people, that the winters in Pennsylvania are less cold, and the summers less warm, than they were forty or fifty years ago. The want of thermometrical observations before and during those years, renders it difficult to decide this question. Perhaps the difference of sensation be|tween youth and old age, with respect to heat and cold, may have laid the foundation of this opinion. I sus|pect the mean temperature of the air in Pennsylvania has not altered, but that the principal change in our climate consists in the heat and cold being less con|fined than formerly to their natural seasons. I adopt the opinion of Doctor Williamson* respecting the di|minution of the cold in the southern, being occasioned by the cultivation of the northern parts of Europe; but no such cultivation has taken place in the coun|tries which lie to the north-west of Pennsylvania, nor do the partial and imperfect improvements which have been made in the north-west parts of the state, ap|pear to be sufficient to lessen the cold, even in the Page 63 city of Philadelphia. I have been able to collect no facts, which dispose me to believe that the winters were colder before the year 1740, than they have been since. In the memorable winter of 1739, 40, the Delaware was crossed on the ice in sleighs on the 5th of March, old style, and did not open till the 13th of the same month. The ground was covered during this winter with a deep snow, and the rays of the sun were con|stantly obscured by a mist, which hung in the upper regions of the air. In the winter of 1779, 80, the river was navigable on the 4th of March; the depth of the snow was moderate, and the gloominess of the cold was sometimes suspended for a few days by a cheerful sun. From these facts, it is probable the winter of 1739, 40, was colder than the winter of 1779, 80.
HAVING premised these general remarks, I pro|ceed to observe, that there are seldom more than twen|ty or thirty days in summer or winter in Pennsylvania in which the mercury rises above 80° in the former, or falls below 30° in the latter season. Some old peo|ple have remarked that the number of extremely cold and warm days in successive summers and winters, bears an exact proportion to each other. This was strictly true in the years 1787 and 1788.
THE warmest part of the day in summer is at two, in ordinary, and at three o'clock in the afternoon in extremely warm weather. From these hours the heat gradually diminishes till the ensuing morning. The coolest part of the four and twenty hours is at the break of day. There are seldom more than three or four nights in a summer, in which the heat of the air is nearly the same as in the preceding day. After the Page 64 warmest days, the evenings are generally agreeable, and often delightful. The higher the mercury rises in the day time, the lower it falls the succeeding night. The mercury at 80° generally falls to 68°, while it descends, when at 60° only to 56°. This disproportion be|tween the temperature of the day and night, in sum|mer, is always greatest in the month of August. The dews at this time are heavy in proportion to the cool|ness of the evening. They are sometimes so consider|able as to wet the cloaths; and there are instances in which marsh-meadows, and even creeks which have been dry during the summer, have been supplied with their usual waters from no other source than the dews which have fallen in this month, or in the first weeks of September.
THERE is another circumstance connected with the one just mentioned, which contributes very much to mitigate the heat of summer, and that is, it seldom continues more than two or three days without being succeeded with showers of rain, accompanied some|times by thunder and lightning, and afterwards by a north-west wind, which produces a coolness in the air that is highly invigorating and agreeable.
THE warmest weather is generally in the month of July. But intensely warm days are often felt in May, June, August and September. In the annexed table of the weather for the year 1787, there is an exception to the first of these remarks. It shews that the mean heat of August was greater by a few degrees than that of July.
THE transitions from heat to cold are often very sudden, and sometimes to very distant degrees. After Page 65 a day in which the mercury has stood at 86° and even 90°, it sometimes falls in the course of a single night to the 65th, and even to the 60th degree, insomuch that fires have been found necessary the ensuing morning, especially if the change in the temperature of the air has been accompanied by rain and a south-east wind. In a summer month in the year 1775, the mercury was observed to fall 20° in an hour and an half. There are few summers in which fires are not agreeable du|ring some parts of them. My ingenious friend Mr. David Rittenhouse, whose talent for accurate observa|tion extends alike to all subjects, informed me, that he had never passed a summer, during his residence in the country, without discovering frost in every month of the year, except July.
THE weather is equally variable in Pennsylvania du|ring the greatest part of the winter. The mercury fell from 37° to 4½° below 0, in four and twenty hours, between the fourth and fifth of February 1788. In this season nature seems to play at cross-purposes. Heavy falls of snow are often succeeded in a few days by a general thaw, which frequently in a short time leaves no vestige of the snow. The rivers Delaware, Schuylkill and Susquehannah have sometimes been frozen (so as to bear horses and carriages of all kinds) and thawed so as to be passable in boats, two or three times in the course of the same winter. The ice is formed for the most part in a gradual manner, and seldom till it has been previously chilled by a fall of snow. Sometimes its production is more sudden. On the 31st of December 1764, the Delaware was com|pletely frozen over between ten o'clock at night and eight the next morning, so as to bear the weight of a man. An unusual vapor like a fog was seen to rise Page 66 from the water, in its passage from a fluid to a solid state.
THIS account of the variableness of the weather in winter, does not apply to every part of Pennsylvania. There is a line, about the 41° of the state, beyond which the winters are steady and regular, insomuch that the earth there is seldom without a covering of snow during the three winter months. In this line the cli|mate of Pennsylvania forms a union with the climate of the eastern and northern states.
THE time in which frost and ice begin to shew themselves in the neighbourhood of Philadelphia, is generally about the latter end of October or the be|ginning of November. But the intense cold seldom sets in till about the 20th or 25th of December; hence the common saying,
As in summer there are often days in which fires are agreeable, so there are sometimes days in winter in which they are disagreeable. Vegetation has been observed in all the winter months. Garlic was tasted in butter in January 1781. The leaves of the wil|low, the blossoms of the peach tree, and the flowers of the dandelion and the crocus, were all seen in Fe|bruary 1779; and I well recollect, about thirty-two years ago, to have seen an apple-orchard in full bloom, and small apples on many of the trees, in the month of December.
Page 67 A COLD day in winter is often succeeded by a mo|derate evening. The coldest part of the four and twenty hours is generally at the break of day.
IN the most intense cold which has been recorded in Philadelphia, within the last twenty years, the mer|cury stood at 5° below 0. But it appears from the accounts published by Messieurs Mason and Dixon, in the 58th volume of the transactions of the Royal So|ciety of London, that the mercury stood at 22° be|low 0 on the 2d of January 1767, at Brandywine, about thirty miles to the westward of Philadelphia. They inform us, that on the first of the same month the mercury stood at 20°, and on the day before at 7° below 0. I have to lament that I am not able to procure any record of the temperature of the air in the same year in Philadelphia. From the variety in the height and quality of the soil, and from the difference in the currents of winds and the quantity of rain and snow which fall in different parts of the state, it is very probable this excessive cold may not have extended thirty miles from the place where it was perceived.
THE greatest degree of heat upon record in Phila|delphia, is 95°.
THE standard temperature of the air in the city of Philadelphia is 52½°, which is the temperature of our deepest wells, as also the mean heat of our common spring water.
THE spring in Pennsylvania is generally less plea|sant, than in many other countries. In March the weather is stormy, variable and cold. In April, and Page 68 sometimes in the beginning of May, it is moist, and ac|companied by a degree of cold which has been called rawness, and which from its disagreeable effects upon the temper has been called the sirocco of this country. From the variable nature of the weather in the spring, vegetation advances very differently in different years. The colder the spring, the more favourable it proves to the fruits of the earth. The hopes of the farmer from his fruit-trees in a warm spring are often blast|ed by a frost in April and May. A fall of snow is remembered with regret by many of them on the night between the third and fourth of May in the year 1774. The colder the winter, the greater delay we observe in the return of the ensuing spring.
SOMETIMES the weather during the spring months is cloudy and damp, attended occasionally with a gentle fall of rain resembling the spray from a cataract of water. A day of this species of weather is called, from its resem|blance to a damp day in Great-Britain, "an English day." This damp weather seldom continues more than three or four days. The month of May 1786, will long be remembered, for having furnished a very un|common instance of the absence of the sun for fourteen days, and of constant damp or rainy weather.
THE month of June is the only month in the year which resembles a spring month in the southern coun|tries of Europe. The weather is then generally tem|perate, the sky is serene, and the verdure of the coun|try is universal and delightful.
THE autumn is the most agreeable season in the year in Pennsylvania. The cool evenings and mornings, which generally begin about the first week in Septem|ber, Page 69 are succeeded by a moderate temperature of the air during the day. This species of weather continues with an increase of cold scarcely perceptible, till the middle of October, when the autumm is closed by rain, which sometimes falls in such quantities as to produce destructive freshes in the rivers and creeks, and some|times descends in gentle showers, which continue with occasional interruptions by a few fair days, for two or three weeks. These rains are the harbingers of the winter, and the Indians have long ago taught the in|habitants of Pennsylvania, that the degrees of cold du|ring the winter, are in proportion to the quantity of rain which falls during the autumn*.
FROM this account of the temperature of the air in Pennsylvania, it is evident that there are seldom more than four months in which the weather is agreeable without a fire.
IN winter, the winds generally come from the north-west in fair, and from the north-east in wet weather. The north-west winds are uncommonly dry as well as cold. It is in consequence of the violent action of these winds that trees have uniformly a thicker and more compact bark on their northern, than on their southern exposures. Even brick houses are affected Page 70 by the force and dryness of these north-west winds: hence it is much more difficult to demolish the north|ern than the southern walls of an old brick house. This fact was communicated to me by an eminent bricklayer in the city of Philadelphia.
THE winds in fair weather in the spring, and in warm weather in the summer, blow from the south-west and from west-north-west. The raw air before mentioned, comes from the north-east. The south-west winds likewise usually bring with them those show|ers of rain in the spring and summer, which refresh the earth. They moreover moderate the heat of the weather, provided they are succeeded by a north-west wind. Now and then showers of rain come from the west-north-west.
THERE is a common fact connected with the ac|count of the usual winds in Pennsylvania, which it may not be improper to mention in this place. While the clouds are seen flying from the south-west, the scud, as it is called, or a light vapor, is seen at the same time flying below the clouds from the north-east.
THE moisture of the air is much greater than for|merly, occasioned probably by the exhalations which in former years fell in the form of snow, now descend|ing in the form of rain. The depth of the snow is sometimes between two and three feet, but in general it seldom exceeds between six and nine inches.
HAIL frequently descends with snow in winter. Once in four or five years large and heavy showers of hail fall in the spring and summer. They generally run in narrow veins (as they are called) of thirty or Page 71 forty miles in length, and two or three miles in breadth. The heaviest shower of hail that is remembered in Phi|ladelphia, did not extend in breadth more than half a mile north and south. Some of the stones weighed half an ounce. The windows of many houses were broken by them. This shower fell in May 1783.
FROM sudden changes in the air, rain and snow often fall together, forming what is commonly called sleet.
IN the uncultivated parts of the state, the snow sometimes lies on the ground till the first week in April. The backwardness of the spring has been ascrib|ed to the passage of the air over the undissolved beds of snow and ice which usually remain, after the winter months are past, on the north-west grounds and wa|ters of the state, and of the adjacent country.
THE dissolution of the ice and snow in the spring, is sometimes so sudden as to swell the creeks and ri|vers in every part of the state to such a degree, as not only to lay waste the hopes of the husbandman from the produce of his lands, but in some instances to sweep his barns, stables, and even his dwelling house into their currents*. The wind during a general thaw, comes from the south-west or south-east.
Page 72 THE air, when dry in Pennsylvania, has a peculiar elasticity, which renders the heat and cold less insup|portable than the same degrees of both are in moister countries. It is in those cases only when summer showers are not succeeded by north-west winds, that the heat of the air becomes oppressive and distressing, from being combined with moisture.
Page 73 FROM tradition, as well as living observation, it is evident, that the waters in many of the creeks in Pennsylvania have diminished considerably within the last fifty years. Hence many mills, erected upon large and deep streams of water, now stand idle in dry wea|ther; and many creeks, once navigable in large boats, are now impassable, even in canoes. This diminution of the waters has been ascribed to the application of a part of them to the purpose of making meadows.
THE mean elevation of the barometer in Philadel|phia, is about 30 inches. The variations in the baro|meter are very inconsiderable in the greatest changes of the weather, which occur in the city of Philadelphia. During the violent and destructive storm which blew from the south-west on the 11th of November 1788, it suddenly fell from 30 to 29 3/10. Mr. Rittenhouse in|forms me, that long and faithful observations have satisfied him, that the alterations in the height of the mercury in the barometer do not precede but always succeed changes in the weather. It falls with the south and south-west, and rises with the north and north-west winds.
THE quantity of water which falls in rain and snow, one year with another, amounts to from 24 to 36 inches. But to complete the account of variable qualities in the climate, it will be necessary to add, that our summers and autumns are sometimes marked by a deficiency, or by an excessive quantity of rain. The summer and au|tumn of 1782 were uncommonly dry, Near two months elapsed without a single shower of rain. There were only two showers in the whole months of Septem|ber and October. In consequence of this dry wea|ther, there was no second crop of hay. The Indian Page 74 corn failed of its increase in many places, and was cut down for food for cattle. Trees newly planted, died. The pasture fields not only lost their verdure, but threw up small clouds of dust when agitated by the feet of men, or beasts. Cattle in some instances were driven many miles to be watered, every morning and evening*. The earth became so inflammable in some places, as to burn above a foot below its surface. A complete consumption of the turf by an accidental fire kindled in the adjoining state of New-Jersey, spread terror and distress through a large tract of country. Crabs which never forsake salt or brackish water, were caught more than a mile above the city of Philadelphia, in the river Delaware, which is 60 miles above the places in which they are usually found. Springs of water and large creeks were dried up in many parts of the state. Rocks appeared in the river Schuylkill which had never been observed before, by the oldest persons then alive. On one of them were cut the figures 1701. The atmosphere, during part of this dry weather, was often filled, especially in the mornings, with a thin mist†, which while it deceived with the expectation of rain, served the valuable purpose of abating the heat of the sun. I am sorry that I am not able to furnish the mean heat of each of the summer months. My notes of the weather enable me to add nothing further upon this subject, than that the summer was "uncommon|ly cool."
Page 75 THE summer of the year 1788 afforded a remark|able instance of excess in the quantity of rain, which sometimes falls in Pennsylvania. Thirteen days are marked with rain in July in the records of the weather kept at Spring-Mill. There fell on the 18th and 19th of August seven inches of rain in the city of Philadelphia. The wheat suffered greatly by the constant rains of July in the eastern and middle parts of the state. So un|productive a harvest in grain, from wet weather, had not been known, it is said, in the course of the last 70 years. The heat of the air during these summer months was very moderate. Its mean temperature at Spring-Mill was 67, 8 in June, 74, 7 in July, and only 70, 6 in August.
IT is some consolation to a citizen of Pennsylvania, in recording facts which seem to militate against our climate, to reflect, that the difference of the weather in different parts of the state at the same season, is hap|pily accommodated to promote an increase of the same objects of agriculture; and hence a deficiency of crops has never been known in any one year throughout the whole state.
THE aurora borealis and meteors are seen occasion|ally in Pennsylvania. In the present imperfect state of our knowledge of their influence upon the human body, it will be foreign to the design of this history of our climate to describe them.
STORMS and hurricanes are not unknown in Penn|sylvania. They occur once in four or five years, but they are most frequent and destructive in the autumn. They are generally accompanied by rain. Trees are torn up by the roots, and the rivers and creeks are Page 76 sometimes swelled so suddenly as to do considerable damage to the adjoining farms. The wind, during these storms, generally blows from the south-east and south-west. In the storms which occurred in Septem|ber 1769, and in the same month of the year 1785, the wind veered round contrary to its usual course, and blew from the north.
AFTER what has been said, the character of the climate of Pennsylvania may be summed up in a few words. There are no two successive years alike. Even the same successive seasons and months differ from each other every year. Perhaps there is but one steady trait in the character of our climate, and that is, it is uniform|ly variable.
TO furnish the reader with a succinct view of the weather in Pennsylvania, that includes all the article that have been mentioned, I shall here subjoin a table containing the result of meteorological observations made near the river Schuylkill, for one year, in the neighbourhood of Philadelphia, by an ingenious French gentleman*, who divides his time between rural em|ployments and useful philosophical pursuits. This table is extracted from the Columbian magazine for Febru|ary 1788. The height of Spring-Mill above the city of Philadelphia, is supposed to be about 70 feet.
|MONTH.||THERMOMETER.||BAROME|TER.||PREVAILING WIND.||DAYS||WATER of RAIN and SNOW,||WEATHER.|
|of Farenheit, mean degree||de Reaumur, degrés moyens||mean height||of aur. boreal.||of rain.||of thunder.||of snow.||of tempest.|
|January||35||1||1||4||29||9||9||Variable still.||7||1||4||3||10||10||Fair, still, cold, and snow.|
|April||54||3||9||9||29||9||6||Still, SW||3||2||1||2||1||2||13||Fair, and very dry.|
|May||61||2||13||29||9||2||Still, WSW||1||14||6||2||4||11||4||Foggy, cold and wet.|
|June||70||7||17||2||29||8||2||WNW||9||1||1||10||4||Very fair and growing weather.|
|July||72||2||17||9||29||9||10||W. WSW vari.||1||5||2||3||1||11||Fair and overcast.|
|August||74||5||18||9||29||10||6||W||11||4||1||5||2||3||Very fair and cloudy.|
|October||51||1||8||5||29||11||9||WNW variable||1||4||7||10||Foggy, fair and dry weather.|
|November||45||1||5||8||29||11||1||Still, variable||1||5||2||6||10||Very fair.|
|December||34||0||29||7||7||WNW||1||1||9||Very fair and very dry.|
|RESULT.||10 Feb. greatest D. of cold.||10 Feb. D. du plus gr. froid.||8 Mar. great|est elevation.||WNW||4||73||17||12||9||32||8||14||TEMPERATURE OF THE YEAR 1787, Very fair, dry, abundant in every thing, and healthy.|
|3 July greatest D. of heat.||3 July plus G. D. de chaud.||2 Febr. least elevation.|
Page 78 IT is worthy of notice, how near the mean heat of the year, and of the month of April, in two successive years, are to each other in the same place. The mean heat of April 1787 was 54° 3, that of April 1788 was 52° 2. By the table of the mean heat of each month in the year, it appears that the mean heat of 1787 was 53° 5 at Spring-Mill.
THE following accounts of the climates of Pekin and Madrid, which lie within a few minutes of the same latitude as Philadelphia, may serve to shew how much climates are altered by local and relative circumstances. The account of the temperature of the air at Pekin, will serve further to shew, that with all the advanta|ges of the highest degrees of cultivation which have taken place in China, the winters are colder, and the summers warmer there than in Pennsylvania, princi|pally from a cause which will probably operate upon the winters of Pennsylvania for many centuries to come, viz. the vicinity of an uncultivated north-west country.
"PEKIN, lat. 39° 54′, long. 116° 29′ W.
"BY five years observations its annual mean tempe|rature was found to be 55°, 5.
- January 20°, 75
- February 32
- March 48
- April 59
- May 72
- June 83, 75
- July 84°, 8
- August 83
- September 63
- October 52
- November 41
- December 27
"THE temperature of the Atlantic under this paral|lel is 62, but the standard of this part of the globe is Page 79 the North Pacific, which is here 4 or 5 degrees colder than the Atlantic. The Yellow Sea is the nearest to Pekin, being about 200 miles distant from it; but it is itself cooled by the mountainous country of Co|rea, which interposes between it and the ocean, for a considerable part of its extent. Besides, all the nor|thern parts of China (in which Pekin lies) must be cooled by the vicinity of the mountains of Chinese Tartary, among which the cold is said to be excessive.
"THE greatest cold usually experienced during this period, was 5°, the greatest heat, 98°: on the 25th of July 1773, the heat arose to 108° and 110°; a N. E. or N. W. wind produces the greatest cold, a S. or S. W. or S. E. the greatest heat*.
"MADRID, lat. 40° 25′ long. 3° 20′ E.
"THE usual heat in summer is said to be from 75 to 85°; even at night it seldom falls below 70°; the mean height of the barometer is 27,96. It seems to be about 1900 feet above the level of the sea†."
THE above accounts are extracted from Mr. Kir|wan's useful and elaborate estimate of the temperature of different latitudes.
THE history which has been given of the climate of Pennsylvania, is confined chiefly to the country on the east side of the Allegany mountain. On the west side of this mountain, the climate differs materially from that of the south-eastern parts of the state in the tem|perature of the air, in the effects of the winds upon the Page 80 and in the quantity of rain and snow, which falls every year. The winter seldom breaks up on the mountains before the 25th of March. A fall of snow was once perceived upon it, which measured an inch and an half on the 11th day of June. The trees which grow upon it are small, and Indian corn is with difficulty brought to maturity even at the foot of the east side of it. The south-west winds on the west side of the mountain are accompanied by cold and rain. The soil is rich, consisting of near a foot in many places of black mould. The roads in this country are muddy in winter, but seldom dusty in summer. The arrange|ment of the strata of the earth on the west side, differs materially from their arrangement on the east side of the mountain.
THE temperature of the air on the west is seldom so hot, or so cold, as on the east side of the mountain. By comparing the state of a thermometer examined by Doctor Bedford at Pittsburgh, 284 miles from Philadel|phia, it appears that the weather was not so cold by twelve degrees in that town, as it was in Philadelphia, on the 5th of February 1788.
TO shew the difference between the weather at Spring-Mill and in Pittsburgh, I shall here subjoin an account of it, in both places, the first taken by Mr. Legeaux, and the other by Doctor Bedford. This account is un|fortunately Page 81 confined only to the first fifteen days in April 1788; but it affords a good specimen of the dif|ference of the weather, on the two sides of the moun|tain, in every month of the year. It is remarkable that in five days out of seven, the rain which fell, was on the same days in both places.
|METEOROLOGICAL OBSERVATIONS, made at SPRING-MILL, 13 Miles NNW of Philadelphia. Month of April, 1788.|
|D. of the month.||THERMOMETER.||BAROME|TER.||PREVAILING WIND.||DAYS||WATER of RAIN and SNOW,||WEATHER.|
|of Farenheit, mean degree||de Reaumur, degrés moyens||mean height||of aur. boreal.||of rain.||of thunder.||of snow.||of tempest.|
|2||46||9||6||6||30||1||Calm.||Overcast and windy.|
|7||51||3||8||6||30||2||N E||1||2||7||Overcast, rainy.|
|13||60||5||12||7||29||10||3||S W||Very fair.|
|14||50||2||8||1||29||9||E||1||1||14||Fair, overcast, rainy.|
|15||58||1||11||6||29||7||7||S W||1||2||13||Foggy, rainy.|
|METEOROLOGICAL OBSERVATIONS, made at PITTSBURGH, 284 Miles from Philadelphia. Month of April, 1788.|
|2||42||N E b N||Clear.|
|5||80||S E b S||1||1||Cloudy.|
|7||48||N E b N||Cloudy.|
|8||66||S E b S||1||1||Cloudy.|
|9||56||N W b N||Cloudy.|
|10||60||S W||Cloudy, with wind.|
|12||67||S W||Cloudy, with wind.|
Page 83 FROM a review of all the facts which have been mentioned, it appears that the climate of Pennsylvania is a compound of most of the climates in the world. Here we have the moisture of Britain in the spring, the heat of Africa in summer, the temperature of Italy in June, the sky of Egypt in the autumn, the cold and snows of Norway, and the ice of Holland in the winter, the tempests (in a certain degree) of the West-Indies in every season, and the variable winds and weather of Great-Britain in every month of the year.
FROM this history of the climate of Pennsylvania, it is easy to ascertain what degrees of health, and what dis|eases prevail in the state. As we have the climates, so we have the health, and the acute diseases, of all the coun|tries that have been mentioned. Without attempting to enumerate the diseases, I shall only add a few words upon the time and manner in which they are produced.
I. IT appears from the testimonies of many aged persons, that pleurisies and inflammatory disorders of all kinds, are less frequent now than they were forty and fifty years ago.
II. IT is a well known fact, that intermitting and bilious fevers have increased in Pennsylvania in pro|portion as the country has been cleared of its wood, in many parts of the state.
III. IT is equally certain that these fevers have les|sened, or disappeared, in proportion as the country has been cultivated.
IV. HEAVY rains and freshes in the spring seldom produce fevers, unless they are succeeded by unseason|ably warm weather.
Page 84 V. HEAVY rains, or frost, in the autumn, alike check the progress of fevers in Pennsylvania.
VI. THE same state of the atmosphere, whether cold or warm, moist or dry, continued for a long time without any material changes, is always healthy. Acute and inflammatory fevers were in vain looked for in the cold winter of 1779, 80. The dry summer of 1782, and the wet summer of 1788, were likewise un|commonly healthy in the city of Philadelphia. These facts extend only to those diseases which depend upon the sensible qualities of the air. Diseases from mi|asmata and contagion, are less influenced by the uni|formity of the weather. The autumn of 1780 was very sickly in Philadelphia, from the peculiar situati|on of the grounds in the neighbourhood of the city, while the country was uncommonly healthy. The dry summer and autumn of 1782 were uncommonly sickly in the country, from the extensive sources of morbid exhalations which were left by the diminution of the waters in the creeks and rivers. The city of Philadel|phia owed its peculiar healthiness during these two sea|sons, to its being nearly surrounded by tide water.
VII. DISEASES are often generated in one season and produced in another. Hence we frequently observe fevers of different kinds to follow every species of the weather that was mentioned in the last observation.
VIII. THE fevers which accompany, or follow a warm summer, are bilious and remitting. In propor|tion as the cool weather advances, they put on the type of Doctor Cullen's typhus mitior. After a very cold winter, I have twice seen pleurisies in the spring, accompanied by the symptoms of the bilious fever. In Page 85 one of those epidemics, the pulse, on the fifth day, in several cases, became irregular, and stopped after every third or fourth stroke. This complication of typhus with synocha, is not peculiar to Pennsylvania. I have been informed that fevers of even a putrid kind frequently succeed long and cold winters in Russia and Sweden. They have been ascribed, by a Russian phy|sician, to extreme cold producing the same sedative effects as extreme heat upon the human body.
IX. THE excessive heat in Pennsylvania has some|times proved fatal to persons who have been much ex|posed to it. Its morbid effects discover themselves by a difficulty of breathing, a general langour, and in some instances, by a numbness and an immobility of the extremities. The excessive cold in Pennsylvania has more frequently proved fatal, but it has been chief|ly to those persons who have sought a defence from it, by large draughts of spirituous liquors. Its operation in bringing on sleepiness previous to death, is well known. On the 5th of February 1788, many people were af|fected by the cold. It produced a pain in the head; and in one instance, a sickness at the stomach, and a vomiting appeared to be the consequence of it. I have frequently observed that a greater number of old peo|ple die, during the continuance of extreme cold, and warm weather, than in the same number of days, in moderate weather.
X. MAY and June are usually the healthiest months in the year.
XI. THE influence of the winds upon health, depends very much upon the nature of the country over which they pass. Winds which pass over mill-dams and marshes in August and September, generally carry with them the seeds of fevers.
Page 86 XII. THE country in the neighbourhood of Phila|delphia is much more sickly than the central parts of the city, after the 20th of August.
XIII. THE night-air is always unwholesome from the 20th of August, especially during the passive state of the system in sleep. The frequent and sudden changes of the air from heat to cold, (exclusive of its insensible qualities) render it unsafe at any time to sleep with open windows.
XIV. PHILADELPHIA became unusually sickly after the year 1778, during the late war, in consequence of the meadows being overflowed to the southward of the city, and of the cutting down of the trees by the British army, which formerly sheltered the city from the exhalations of the grounds to the north and north-west. From the repairs of the banks of the meadows, which exclude tides and freshes; from the cultivation of the grounds to the westward of the city, which were for|merly covered with filth, or with stagnating waters; and lastly, from the more regular cleaning of the streets, and the enclosure of a large and offensive canal which crossed two of the principal streets near the centre of the city, Philadelphia, from having been formerly the most sickly, has become one of the healthiest cities in the United States.
XV. VALETUDINARIANS always enjoy the most health in Pennsylvania in the summer and winter months. The spring, in a particular manner, is very unfavourable to them.
I SHALL conclude the account of the influence of the climate of Pennsylvania upon the human body, with the following observations.
Page 87 1. THE sensations of heat and cold are influenced so much by outward circumstances, that we often mis|take the degrees of them, by neglecting to use such conveniencies as are calculated to obviate the effects of their excess. A native of Jamaica often complains less of the heat, and a native of Canada of the cold, in their respective countries, than they do under cer|tain circumstances in Pennsylvania. Even a Pennsyl|vanian frequently complains less of the heat in Ja|maica, and of the cold in Canada, than in his native state. The reason of this is plain. In countries where heat and cold are intense and regular, the inhabitants guard themselves by accommodating their houses and dresses to each of them. The instability and short du|ration of excessive heat and cold in Pennsylvania, have unfortunately led its inhabitants, in many instances, to neglect adopting customs, which are used in hot and cold countries to guard against them. Where houses are built with a southern or south-western front expo|sure, and where other accommodations to the climate are observed in their construction, the disagreeable ex|cesses of heat and cold are rendered much less percep|tible in Pennsylvania. Perhaps the application of the principles of philosophy and taste to the construction of our houses within the last thirty or forty years, may be another reason why some old people have supposed that the degrees of heat and cold are less in Pennsyl|vania than they were in former years.
2. THE number, height, and vegetable producti|ons of the mountains in Pennsylvania, afford a fa|vourable prognosis of the future healthiness of the state. Exclusive of the beneficial effects of these moun|tains in producing salutary winds, and gentle rains, they will serve as a perpetual and inexhaustible store|house Page 88 of that pure species of air, which has of late been proved to constitute the vital part of common air.
3. THE variable nature of the climate of Pennsyl|vania does not render it necessarily unhealthy. Doc|tor Huxham has taught us, that the healthiest seasons in Great-Britain have often been accompanied by the most variable weather. His words upon this subject convey a reason for the fact.