of the United States.  It is on the edge of this district, and visibly under its influence, that the State of Minnesota, for the most part, lies.  But we pass, for the present, to the brief consideration of the third grand division, embracing the entire country east of a line drawn from near Central Texas to the centre of Wisconsin, including the immediate region surrounding all the great lakes.  Here we have an association of elements constituting a highly variable climate, which prevails over all its surface at all seasons, with remarkable uniformity.  The wide range in both vegetable and animal life over this area is one of its chief distinguishing characteristics, partaking of the semi-tropical on the one hand, with a low winter temperature on the other, but traversing neither range so far as to prove directly destructive in its effects.  All over this eastern area are scattered lakes and rivers, with an ocean boundary line, and uniform forest ranges with a great variety of deciduous trees known to the temperate and sub-tropical latitudes; and it is quite remarkable to note that some of the latter forms extend in their acclimation to near the northern boundary lines of the Union, while the pine, walnut, and chestnut may be found at or near the extreme southern limits.

In all of these three grand divisions of climate, however, exceptional localities exist where there is a marked nonconformity to the prevailing characteristics.  The peninsula of Florida is such an exception, owing to its peculiar location, and the great humidity of its atmosphere during a considerable fraction of the year.  Here we have a fully developed season of periodical rains, beginning usually in June and ending in the latter part of September.  The winter is the dry season, being contrary to the general rule applying to tropical and sub-tropical areas, and forms, with the mild temperature, the principal ground for the reputation which that State has as a resort for special classes of invalids.[B]

The sudden and extreme variations of temperature in this eastern climatic tract, whether from local disturbing causes, as is not unfrequently the case, or otherwise, are usually accompanied by cold draughts of air, chilling and generating all manner of ills, of which rheumatism and consumption are the separate and highest types.

While it is generally understood that the prevailing winds of the whole continent embraced within the limits of the United States are uniformly from the west, still, over this eastern division, counter-winds of a lower character disturb, modify, and elevate the course of this great westerly current, giving rise to the exceeding variability of the surface winds, which, as is well known, may blow within the brief space of twenty-four hours from all directions of the compass, at almost any time and point whatsoever.