A glance upon the map will convince any one, that it is with us that the weather is most changeable. The reasons for this may now be more closely examined. Our country lies nearly half way between the pole and the equator. From our pole we constantly receive a cold wind, the north wind. And above, in the atmosphere, a warm wind, the south wind, goes continually from the equator to the pole. Through the rotation of the earth around its axis from west to east, the north wind becomes an easterly, that is, a northeast wind; and the south wind in the upper atmosphere becomes a westerly, or southwest wind. The former, coming from cold countries, carries no vapor with it; hence, during northeast wind we have clear sky, or sunshine, but without heat. If this wind occurs in winter, it brings us dry frost; in daytime the sun shines splendidly, at night the stars sparkle brilliantly; yet our breath freezes on our lips. The same wind when prevailing in the first days of spring, causes us, in spite of the glaring sun, to feel considerably cold in the shade. And it is but natural that it should be so. The wind comes from the north; there ice and snow are just melting, and the sun's heat being employed for this "melting business," the air cannot receive much of it. This kind of weather would be regular with us; but, as we know already, the heated upper air flows from the equator to the north pole; now we live in the very region where this upper air, in its descent towards the poles, at times touches the surface of the earth, thus causing warm currents of air, which occasionally are followed by cold ones. Near the equator the cold current of air moves below and the warm one above; while in our regions, both currents meet near the surface of the earth, struggle with each other, seek to repel one another, rush and roll in all directions over the land, and bring us such varieties of weather as will exasperate all weather prophets, and greatly increase the difficulty of scientific solutions in meteorology. In the next chapter we shall endeavor to prove that this state of affairs, together with the situation of our country, are the main causes of the changeableness of our weather. CHAPTER X. THE CHANGEABLENESS OF THE WEATHER WITH REGARD TO OUR GEOGRAPHICAL POSITION.