SECT. V.] GENERAL OBSERVATIONS. 137 variations produced by a different configuration of the surface of the earth, and by the difference in the general course of the great chains of mountains in the two hemispheres, the most probable general cause will be found in the great prevalence of the western winds throughout the Northern Temperate Zone. The fact is fully ascertained, and is the cause of a dif- ference amounting to about one third in the length of the pas- sages between Europe and America. Those winds reach the western coasts of both, after having crossed the Atlantic or the Pacific Ocean, and with a temperature corresponding with that of the sea. The same winds, on the eastern coasts of Asia and of America, are land winds, and bring with them, especially in winter, when they come from the northwest, the temperature of the country where they originated. If the trade-winds of the Torrid produce a counter-current in the atmosphere of the Temperate Zone, the rotatory motion of the earth and the effect of the solar heat may be assigned as the primary cause of the difference of climate to which we allude. Whatever that cause may be, there cannot be any expectation of a permanent change in that respect. It is not indeed per- ceived, how cultivation could make any sensible alteration ; and it is ascertained that the absence of trees produces none.* But the difference between the forest and the prairie country had a greater influence on the means of subsistence and the habits of the Indians, than even that of climate. The whole country, east of the Alleghany Mountains, was covered with a dense and uninterrupted forest, when the European settlers landed in America. South of the fortieth degree of latitude, it extends in the same manner, as far west as the Mississippi, without any other considerable exception, than a tract called " the Barrens," situated in the vicinity of the river of that name in the State of Kentucky. But, between that latitude and Lake Erie, some intervals of land destitute of wood, and called " Prairies," begin to appear, as you approach the Scioto, and even more eastwardly in the vicinity of the Lake. These prairies gradually increase in size and in num- ber as you proceed westwardly, and are nearly equal in extent to the forest land, in the northern part of the State of Illinois
- It would seem that the climate of Rome was formerly colder in
winter than now. The account given of that of Paris by the Emperor Julian would nearly answer for the present time. VOL. II. 18
