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give the humid winds as ranging from east round to south-west, largely south-east. This 

 is explained by some who have given thought to the subject as being caused by much 

 moisture passing from the equatorial current, high above us, into lower currents blowing 

 other ways, by the fact that the Eocky Mountains deprive the west wind of much 

 moisture, and by the passage of moisture here across the Atlantic States from the warm 

 Gulf Stream and the Gulf of Mexico. Many acute observers, however, hold strongly to 

 the south-west wind being the rain-bringer. Still from the equator, one way or another, bu* 

 of course from the south, most of our moisture comes. It may be here remarked that in 

 order clearly to comprehend 'the motion of the winds, it is well ever to keep in mind 

 the fundamental law, that all movements of the atmosphere are in consequence of the 

 property gases possess of being expanded by heat, and that the heat of the sun keeps all 

 in motion. ^ 



Here is an instance, from the meteorologist Spang, of the meeting of these two 

 winds forming whirlwinds : — 



" The pblar current, in its course towards the south, held in suspense by the equatorial 

 or warm current, may be compared to a body of water confined by a dam, except that 

 the dam has here also a positive force, and if released, a motion of its own. If this aerial 

 dam is broken at some point on the surface of the earth, the air of the polar current 

 above the break will sink into it, and there will be formed in its upper region a depres- 

 sion or trough corresponding to the break. That portion of the equatorial air which has 

 opposed the sunken polar air will rush with great force into the depression, and produce 

 an eddy or whirl, and cause a rotary storm and a cloud to be formed which assumes the 

 form of an inverted cone. This cloud is formed by the sudden and profuse condensation 

 of the moisture contained in the air of the equatorial current, which is thrown suddenly 

 into higher and colder regions, and sometimes the temperature is So greatly reduced that 

 the vapour, after being condensed freezes, and hail is formed by the centrifugal force of 

 the rotary storm." 



The two winds just described may he said to be the only two winds in the world. 

 All the rest are but modifications of these, occasioned by what may in comparison be 

 considered local causes. The different divisions and apportionments of land and water 

 here and there cause many inferior rarefactions and condensations, which produce all the 

 varied phenomena of tempests, hurricanes, gales hither and thither, which continually 

 take place. This forms a chief part in the great plan of Nature. By this many move- 

 ments necessary in fitting this world for the habitation of beings like ourselves, are set in 

 operation. One very important one, which we shall frequently have occasion to notice, 

 is that by this means is borne upwards from the equatorial seas and towards the poles 

 that vast mass of moisture previously described. It does not of course all go as far as 

 the polar regions, though a great portion does. Much falls back in rain in the tropics, 

 and much on the way north and south. It may be here observed that no doubt large 

 evaporation of water is continually occurring elsewhere, on ocean, lake and river, and on 

 land as well as in the tropical zone. But the last is the chief source of supply. We will 

 now leave this part of the subject and go on to another intimately connected therewith^ 

 which is necessary to be considered before we can make further headway. 



