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 nearly 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 of which includes a distance of two miles from the Delaware. The land near the rivers, between the city and the conflux of the rivers, is in general low, moist, and subject to be overflowed. The greatest part of it is meadow ground. The land to the northward and westward, in the vicinity of the city, is high, and in general 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. The width of the river near the city is about a mile.
The city, with the adjoining districts of Southwark and the Northern Liberties, contains between 70 and 80,000 inhabitants.
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 observations. The winter of the year 1779–80, was uniformly and uncommonly cold. The river Delaware 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 Jersey 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 intenseness of the cold during this winter. The ears of horned cattle and the feet of hogs exposed to the air, were frost-bitten; squirrels perished in their holes, and partridges were often found dead in the neighbourhood of farm houses. The mercury in January stood for several hours at 5° below 0, in Fahrenheit's thermometer; and during the whole of this month (except on one day), it never rose in the city of Philadelphia so high as to the freezing point.
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 thermometer, 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 clothing and sensation between youth and old age, in winter and summer, may have laid the foundation of this opinion. I suspect 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 confined than formerly to their natural seasons. I adopt the opinion of Doctor Williamson[30] respecting the diminution 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 countries 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, appear to be sufficient to lessen the cold, even in the 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 constantly 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 sometime 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.
The winter of 1804–5 exhibited so many peculiarities that it deserves a place in the history of the climate of Pennsylvania. The navigation of the Delaware was obstructed on the 18th of December. The weather partook of every disagreeable and distressing property of every cold climate on the globe. These were intense cold, deep snows, hail, sleet, high winds, and heavy rains. They generally occurred in succession, but sometimes most of them took place in the course of four and twenty hours. A serene and star-light evening, often preceded a tempestuous day. The mercury stood for many days, in Philadelphia, at 4° and 6° above 0 in Fahrenheit's thermometer. The medium depth of the snow was two feet, but from its fall being accompanied with high winds, its height in many places was three and four feet, particularly in roads, which it rendered so impassable, as to interrupt business and social intercourse, in many parts of the state. From the great depth of the snow, the ground was so much protected from the cold, that the frost extended but six inches below its surface. The newspapers daily furnished distressing accounts of persons perishing with the cold by land and water, and of shipwrecks on every part of the coast of the United States. Poultry were found dead, or with frozen feet, in their coops, in many places.