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ILLINOIS STATE HOKTICTTLTURAL SOCIETY. 



had prepared a paper upon the subject, and with special reference to the 

 effects of the wind and the course of the wind upon rainfall. He read 

 as follows : 



Rainfall. — We are living at the bottom of a very deep sea. This sea is the atmos- 

 phere that surrounds the earth. In it we live, move and have our being. It is not only 

 life-sustaining, but life-destroying. It builds up every form of vegetable and animal 

 life, and when death comes it seizes upon these forms and reduces them to their ulti- 

 mate elements again. Our atmosphere is most fickle and inconstant. At one moment 

 it will kiss the cheek of the new-born babe with a mother's tenderness ; at the next, it 

 comes with the destructive hurricane and the death-dealing tornado, uprooting forests, 

 prostrating cities, sweeping as with the besom of destruction over the land, marking its 

 pathway with ruin, desolation and death. The mighty oak, the giant of the forest that 

 has stretched out his arms to wind and tempest for centuries, becomes but idle sport to 

 the angry storm tiend, and strong navies, proud monuments of man's genius, are but 

 bubbles on the stream. 



Extent of our Atmosphere. — The atmosphere is a mobile and all-pervading fluid. 

 There is no nook or corner it does not fill ; no crevice it does not enter. It pervades the 

 depths of the ocean as well as its surface. By reason of its tension it reaches to a great 

 height. Some have estimated its extent two hundred miles. According to the law of 

 decrease of density its height should be infinite. But at the point where the centrifugal 

 force balances the force of gravity there must necessarily be the limit. It may be 

 mathematically demonstrated that the air decreases in density in a geometrical ratio 

 as the altitudes increase in arithmetical ratio. Let us look for a moment at this law of 

 diminution of density. It has been found by actual observation that at a distance of 

 three and a half miles from the surface of the earth its density is diminished one-half. 

 At the distance of seven miles its density is one-fourth ; at ten and one-half miles, 

 one-eighth ; at fifty miles, it is one-sixteen-thousandth of the density at the earth's surface. 



Weight of the Atmosphere. — The weight of the atmosphere has been accurately 

 computed. It will keep in equilibrium a column of mercury about thirty inches in 

 height. Hence its weight is just equal to a stratum of mercury, covering the entire 

 globe, thirty inches in thickness. The earth's atmosphere, therefore, weighs nearly six 

 quadrillion tons. 



Wind. — Wind is air in motion. As regards their general direction, the winds are 

 nearly as regular as the planets in their course. As the preacher hath said, " The wind 

 goeth towards the south, and turneth about unto the north; it whirleth about continually, 

 and the wind returneth again according to his circuits." There are three general systems 

 of winds : the equatorial, the middle latitude and the polar winds. Let us now trace these 

 winds in their circuits. In the region about the equator the sun's rays are nearly 

 vertical, and consequently the air is heated, causing it to rise into the higher regions. 

 It thence flows northward and southward as a high current. When this northern high 

 current reaches about 32 degrees of latitude it meets a high current coming from the 

 north. Both of these currents at this point come down to the earth's surface, forming 

 the " Calms of Cancer," and progress as surface currents — the one that started from the 

 equator as a high current still continues northward as a surface current; the other, 

 which came from the north as a high current, continuing southward to the equator as a 

 surface current. The northward current meets a southward current at about 64 degrees 

 north latitude. Both of these currents at this point rise into the higher regions and 

 become high-moving currents ; the northward-bound still moving northward, the other 

 moving southward. When the northward current arrives at the pole it is precipitated 

 to the earth and becomes a surface current until it reaches 64 degrees of latitude. At 

 this point it rises, moving as a high current to 32 degrees of latitude, the " Calms of 

 Cancer;" there it descends to the earth and moves as a surface current to the equator. 

 Here the air is heated again, causing it to ascend into the higher regions, where it moves 

 as before. A similar phenomenon is to be observed in southern latitudes. Truly the 

 wind "whirleth about continually, and returneth again according to his circuits." 

 Thus we see the winds have their circuits, and they depart from them but a little more 



