At night we returned to Philadelphia.
September the 23d. There are no Hares in this country, but some animals, which are a medium between our Hares and Rabbets, and make a great devastation whenever they get into fields of cabbage and turneps.
Many people have not been able to find out why the North American plants which are carried to Europe and planted there, for [[106]]the greatest part flower so late, and do not get ripe fruit before the frost overtakes them, although it appears from several accounts of travels, that the winters in Pensylvania, and more so those in New York, New England, and Canada, are full as severe as our Swedish winters, and therefore are much severer than those which are felt in England. Several men of judgment charged me for this reason to examine and enquire into this phœnomenon with all possible care. But I shall instead of an answer, rather give a few remarks which I made upon the climate and upon the plants of North America, and leave my readers at liberty to draw the conclusions themselves.
1. It is true, that the winters in Pensylvania, and much more those in the more northern provinces, are frequently as severe as our Swedish winters, and much colder than the English ones, or those of the southern parts of Europe. For I found at Philadelphia, which is above twenty deg. more southerly than several provinces in Sweden, that the thermometer of professor Celsius, fell twenty-four deg. below the freezing point in winter. Yet I was assured that the winters I spent here, were none of the coldest, but only common ones, which I could likewise conclude from the Delaware’s [[107]]not being frozen strong enough to bear a carriage at Philadelphia during my stay, though this often happens. On considering the breadth of the river which I have already mentioned in my description of Philadelphia, and the difference between high and low water, which is eight English feet; it will pretty plainly appear that a very intense frost is required to cover the Delaware with such thick ice.
2. But it is likewise true, that though the winters are severe here, yet they are commonly of no long duration, and I can justly say, that they do not continue above two months and sometimes even less, at Philadelphia; and it is something very uncommon when they continue for three months together, in so much that it is put into the gazettes. Nearer the pole the winters are somewhat longer, and in the quite northern parts they are as long as the Swedish winters. The daily meteorological observations which I have made during my stay in America, and which I intend to annex at the end of each volume of this work, will give more light in this matter.
3. The heat in summer is excessive, and without intermission. I own I have seen the thermometer rise to nearly the same degree at Aobo in Finland. But the difference [[108]]is, that when the thermometer of professor Celsius rose to thirty deg. above the freezing point once in two or three summers at Aobo, the same thermometer did not only for three months together stand at the same degree, but even sometimes rose higher; not only in Pensylvania, but likewise in New York, Albany, and a great part of Canada. During the summers which I spent at Philadelphia, the thermometer has two or three times risen to thirty-six deg. above the freezing point. It may therefore with great certainty be said, that in Pensylvania the greatest part of April, the whole May, and all the following months till October, are like our Swedish months of June and July. So excessive and continued a heat must certainly have very great effects. I here again refer to my meteorological observations. It must likewise be ascribed to the effects of this heat that the common melons, the water melons, and the pumpions of different sorts are sown in the fields without any bells or the like put over them, and yet are ripe as early as July; further, that cherries are ripe at Philadelphia about the 25th. of May, and that in Pensylvania the wheat is frequently reaped in the middle of June.
4. The whole of September, and half, if [[109]]not the whole of October, are the finest months in Pensylvania, for the preceding ones are too hot. But these represent our July and half of August. The greatest part of the plants are in flower in September, and many do not begin to open their flowers before the latter end of this month. I make no doubt that the goodness of the season, which is enlivened by a clear sky, and a tolerably hot sun-shine, greatly contributes towards this last effort of Flora. Yet though these plants come out so late, they are quite ripe before the middle of October. But I am not able to account for their coming up so late in autumn, and I rather ask, why do not the Centaurea Jacea, the Gentiana, Amarella and Centaurium of Linnæus, and the common golden rod, or Solidago Virgaurea flower before the end of summer? or why do the common noble liverwort, or Anemone Hepatica, the wild violets (Viola martia, Linn.) the mezereon (Daphne Mezereum, Linn.) and other plants shew their flowers so early in spring? It has pleased the Almighty Creator to give to them this disposition. The weather at Philadelphia during these months, is shewn by my meteorological tables. I have taken the greatest care in my observations, and have always avoided putting the thermometer [[110]]into any place where the sun could shine upon it, or where he had before heated the wall by his beams; for in those cases my observations would certainly not have been exact. The weather during our September and October is too well known to want an explanation.[15]
5. However there are some spontaneous plants in Pensylvania, which do not every year bring their seeds to maturity before the cold begins. To these belong some species of Gentiana, of Asters, and others. But in these too the wisdom of the Creator has wisely ordered every thing in its turn. For almost all the plants which have the quality of flowering so late in autumn, are perennial, or such as, though they have no seed to propagate themselves, can revive by shooting new branches and stalks from the same root every year. But perhaps a natural cause may be given to account for the late growth of these plants. Before the Europeans came into this country, it was inhabited by savage nations, who practised agriculture but little or not at all, and chiefly [[111]]lived upon hunting and fishing. The woods therefore have never been meddled with, except that sometimes a small part was destroyed by fire. The accounts which we have of the first landing of the Europeans here, shew that they found the country all over covered with thick forests.[16] From hence it follows, that excepting the higher trees, and the plants which grow in the water or near the shore, the rest must for the greatest part have been obliged to grow perhaps for a thousand years together, in a shade, either below or between the trees, and they therefore naturally belong to those which are only peculiar to woody and shady places. The trees in this country drop their leaves in such quantities in autumn, that the ground is covered with them to the depth of four or five inches. These leaves lie a good while in the next summer before they moulder, and this must of course hinder the growth of the plants which are under the trees, at the same time depriving them of the few rays of the sun which can come down to them through the thick leaves at the top of the trees. These causes joined together make such plants flower much later than they would otherwise do. May [[112]]it not therefore be said, that in so many centuries these plants had at last contracted a habit of coming up very late, and that it would now require a great space of time to make them lose this habit, and use them to quicken their growth?
September the 24th. We employed this whole day in gathering the seeds of plants of all kinds, and in putting scarce plants into the herbal.
September the 25th. Mr. Hesselius made me a present of a little piece of petrified wood, which was found in the ground here. It was four inches long, one inch broad, and three lines thick. It might plainly be seen that it had formerly been wood. For in the places where it had been polished, all the longitudinal fibres were easily distinguishable, so that it might have been taken for a piece of oak which was cut smooth. My piece was part of a still greater piece. It was here thought to be petrified hiccory. I afterwards got more of it from other people. Mr. Lewis Evans told me that on the boundaries of Virginia, a great petrified block of hiccory had been found in the ground, with the bark on it, which was likewise petrified.