But how is it that they thus return with such wonderful regularity, in a narrow traveling belt of daily rains within the tropics, and a movable belt of irregular rains without the tropics, extending to the poles, leaving a space on each side of the equator encircling the earth in like manner (except at two points, _viz._, Eastern Asia and Eastern North America), from which they do not go, and to which they do not return, and which is almost entirely unfurnished with rain? And all this without any relation, whatever, to the contiguity of the oceans? Obviously this is not the work of mere evaporation, or of the accidental or irregular commingling of winds with different dew points, or quantities of moisture in solution, or accidental, irregular changes of barometric pressure. _It is one vast, wonderful, connected, and regular system--co-extensive with the globe--necessary to the return of moisture from the oceans upon the most inconsiderable portion of it, and to the condensation of the local moisture of evaporation; and by it the waters are returned from the oceans as regularly and bountifully upon the far interior of the great continents in the same latitudes, as upon the "isles which rest in their bosoms."_ CHAPTER II. Before proceeding to an examination of this connected atmospheric machinery, and an investigation of the particular ocean from which our rivers return, it may be well to look at the form in which they appear to return, that we may have a clear understanding of terms. They seem to return in the form of clouds, and in storms and showers, although, in truth, they return in regular, uniform, ordinarily invisible currents, and the storms and showers are but condensations in, and discharges from portions of those currents, aided by the local moisture of evaporation. The term _storms_, seems to be used by European meteorologists to denote what we term thunder showers or gusts, and tornados; while what we call storms are denominated by them regular rains. As the terms are extensively in use in this country, we must adhere to the meaning attached to them _here_ rather than _there_. Storms with us, then, are regular rains of from six to forty-eight or more hours' continuance: generally without lightning, or thunder, or gusts, and usually with wind of more or less force, from some easterly point. They are called north-east storms, or south-east storms, according to the point from which the surface winds blow. Practically we shall find that this distinction is of some importance, for the north-east storms are the longest, lasting generally twenty-four hours, or more, while the south-east ones seldom, if ever, continue as long.