JAMES HENRY COFFIN. 455 



tance in a straight line, and direction at the end of a given 

 time, from the place of his departure. In this work Prof. 

 Coffin was the first clearly to establish the fact, by accurate 

 comparison of observations, that there are three great zones of 

 winds in the Northern Hemisphere. At a later date he demon- 

 strated the same truth in the case of the Southern Hemisphere. 

 The first belt is that of the region of the easterly trade winds, 

 extending northward in the Western Hemisphere to about the 

 32d degree north latitude, and in Europe to the 426. degree. 

 The second is the great belt around the world of the return 

 trades, in which the predominant direction is from the west. 

 This extends northward in America to 56, and in Europe and 

 Asia to about 66 north latitude. Beyond this, principally 

 within the Arctic Circle, is a belt of easterly or northeasterly 

 winds. The common pole of these belts or zones has not the 

 same position as that of the geometrical pole of the earth. It 

 appears to be in latitude 84 and longitude 105 west of Green- 

 wich, and has been denominated by Prof. Coffin the meteoro- 

 logical pole. 



These results are in general accordance with the mathemat- 

 ical deductions from the theory of the winds of the globe, which 

 considers them as due to the combined action of the movement 

 produced in the air by the greater heat of the equator, and the 

 rotation of the earth on its axis. 



The researches of Prof. Coffin also strikingly exhibit the 

 fact of the influence of the seasons in modifying the direction 

 of the wind, or in producing the results denominated monsoons. 

 Thus, along the eastern coast of North America, as is shown 

 on the maps, the tendency during the summer months of the 

 opposing forces is to lessen the dominant westerly wind, and 

 this effect is noticed even beyond the Mississippi, as well as in 

 the Atlantic Ocean along our coast. The effect is, undoubtedly, 

 due to the change of temperature in the land the temperature 

 of the ocean remaining nearly the same during the year, while 

 that of the land is greatly increased in summer above the 

 mean, and depressed in winter. From this cause the air will 

 tend to flow toward the centre of the continent from the 

 ocean in summer, and from the same centre toward the ocean 

 in winter. 



At the meeting of the American Association for the Ad- 

 vancement of Science, held in Cleveland in 1853, he discussed 



