80 WIND ITS PRIMARY CAUSE: 



in some degree the temperatures of the world, to 

 carry off and distribute moisture where it is required, 

 to sweep away noxious vapours, and generally to 

 ventilate the Earth and gladden the heart of man. 



The primary cause of all wind is the combined 

 action of heat and cold. If the world were heated 

 with perfect equality all round, there would be, as 

 far at least as heat is concerned, a perfect and per- 

 manent stagnation of the atmosphere; and this 

 would speedily result in the destruction of every liv- 

 ing thing. But by the varied arid beautiful arrange- 

 ments which the Almighty has made in nature he 

 has secured a regular flow of atmospheric currents, 

 which will continue unalterably to move as long as 

 the present economy of things exists. The intense 

 and constant action of the sun's rays in the torrid 

 zone produces great heat, while the less powerful 

 and frequently interrupted influence of his rays in 

 the frigid zones induces extreme cold. Hence we 

 have in one region heated air, in another cool air. 

 Now, the effect of heat upon air is to expand it, 

 make it light, and cause it to rise. The moment it 

 does so, the cold air rushes in to supply its place; and 

 this rushing in of tKe cold air is what we call wind. 



It may surprise many people to be told that there 

 are only two great and never-ceasing courses of the 

 winds of this world namely, north and south. 

 They flow perpetually from the equator to the poles, 

 and from the poles to the equator. All the ir- 

 regularities and interruptions that we observe are 



