276 Coffin's Winds of the Globe. 



as the carve more easily formed by joining the four lines, 

 whose direction and length are recorded in the resultants of 

 series I. On the North American coast of the Atlantic the 

 curve is of this general shape W"", while on the European coast 

 iture is reversed, being *~>^. The change seems to 

 mid-ocean at longitude 30° to 35° west. Except 

 where there are marked local obstructions to the free flow of the 

 air, this law seems invariable ; and it holds in the majority of 

 cases, even in the motion of the clouds ; but Mount Washing- 

 ton, New Hampshire, seems a remarkable exception ; the ob- 

 servations for 1870-3 give as resultants — 



Resultants. Ratio. Monsoon influence. 



Spring, N. 87°2l'W. '62 S. 17° 15' W. -13* 



Summer, N. 62° 33' W. -62 N. 12° 30' E. '13 . 



Autumn, N. 60° 46' W. 63| N. 9° 3' E. '15£ 



Winter, N. 87° 38' W. -60 S. 9° 1' W. '13£ 



These S-shaped curves were pointed out and illustrated by 

 Professor Coffin, in 1848, at the same time that he announced 

 the existence of the Polar system of the northeast winds, and 

 the Temperate system of the westerly winds. The forces that 

 deflect the wind from its mean annual direction, and so cause 

 these peculiar curves are given under the title of Monsoon 

 Influences. Are they due to changes in the temperature, or to 

 variations in atmospheric pressure at the different seasons? 

 An examination of the maps shows instantly that in all parts 

 of the globe, these deflecting forces are inclined toward the 

 nearest adjacent land-center in the summer, and toward the center 

 of the nearest large body of water in the winter, thus showing 

 the direct agency of heat in modifying the direction of the cur- 

 rent, and the intensity of its flow. That barometric pressure 

 however plays the more important part in effecting these seasonal 

 changes of direction is shown in Dr. Woeikof s minute discus- 

 sion ; wherein, reproducing the isobaric charts of Dr. Alexander 

 Buchan, he considers the five wind systems in general, and 

 then treats separately the winds in the smaller geographical 

 divisions of the earth. He corrects the error, so generally 

 prevalent, of limiting the monsoons to the tropical part of Asia, 

 showing that they extend as well to all China, Japan, Mant- 

 chooria, the western coast of the Sea of Ochotsk, and the basin 

 of the Amoor river; and, with a reverse of seasons, to Australia- 

 The winds on the whole Atlantic coast of the United States 

 were early shown bv Professor Coffin to possess some monsoon 

 features, though slight. The influence of the Gulf of Mexico 

 over the basin of the Mississippi and Ohio, from latitude 34° to 

 42°, in producing the west-southwest direction of the winds at 

 all seasons, is traced to the coustant maximum pressu 

 to the south and the minimum to the north and northeast. 



