We have endeavored to explain why our weather is so uncertain and incomputable. As we have seen, it has its origin in this, that in our regions the warmer equatorial currents of air no longer move _above_ the colder ones, but that they descend here, and pursue their northern course alongside and opposing the colder currents. This often gives rise to a struggle between cold and warm currents. In summer we witness such combats very frequently. The sky is at first bright; the sun sends down his most powerful rays; in the shade we are refreshed by a strong draught, which keeps the sky clear, and free from clouds. Suddenly there comes a calm. Even in the shade the heat now becomes intolerable. The trees stand immovable; no leaflet stirs. The complete calm becomes unendurable, and causes anxiety. "Always a calm before a storm," say the people, and hasten to seek shelter in their houses--and well! for it is not long before a counter wind commences to blow. The weathercock turns round, the dust in the streets is whirled up in eddies, and here and there rises in clouds to the house-tops. Suddenly clouds are seen to form themselves; the trees shake their crowns; the leaves rustle, and before one is aware of it, we have storm, thunder, and violent rain, which cool off the earth. Whence came this weather; more especially, whence came the calm preceding it, and the whirlwind following? There were two opposite currents of air, which for a time avoided each other, but at length met over our heads. Each current at first pressed on the other with equal force, so that they mutually were brought to a stand-still; this we called a _calm_. But such an equilibrium does not last long, for one current must in the end overcome the other; they whirl through one another, raise the dust in high columns, seize the trees and give them a thorough shaking. The cold current changes the vapor of the warm current into clouds, then into rain. The pouring down rain immediately sets free the heat. At this stage electrical phenomena are witnessed, such as lightnings, claps of thunder, and concussions of the air. And this continues until one current of air has carried the victory over the other; not till then does the weather become quiet again. Besides these opposing currents of air, which come from the north and south, there are other causes disturbing our weather, viz., the geographical position of our country in regard to the east and west.