744 



WINDS OF THE GLOBE. 



INDIAN OCEAN. 



I have given before some figures relating to the northern part of the Indian Ocean. 

 Unfortunately we are for from knowing the winds of this ocean so well as those of 

 the Atlantic. The limits of the trades especially are more uncertain. The posi- 

 tion of the Indian Ocean is such, that only the S. E. trade is developed to its full 

 extent, and in our summer, is attracted towards the heated continent of Asia, and, 

 owing to the rotation of the earth, gradually becomes a S. W. wind. There is no 

 equatorial belt of calms at that season, and a reference to tlie map of isobars, Plate 

 14, will show that pressure increases then from the polar limits of the S. E. trade, 

 about 25° S. uninterruptedly to the continent of Asia. This is .also the explana- 

 tion of the S. W. Monsoon, which is only the deflected S. E. trade. 



Even in our winter (December to February) the winds in the Indian Ocean are 

 under the influence of continents. In the northern part the winds are N. W., that is 

 the N. E. trade crosses the equator, and is drawn towards the heated continent of 

 Australia. Nearer to Africa, the winds are N. E. at this season, also occasioned by 

 a deflection of the trade-wind towards the tropical and sub-tropical part of Africa. 

 Thus, on the whole, the Indian Ocean is more under the influence of the conti- 

 nents than the Atlantic. The following table gives the direction of the winds: — 







June to Aufjust. 



December to l-"cbru.iry. 1 





w 





« 





^ 





^ 





W 





H 





i 





^ 







^ 



^ 



H 



aj 



0! 



aj 



^ 



fe 



lei 

 22 



15 

 32 



Is 



10 



2 



1 



1 



4 



Zone 23. 



Indian Ocean, 47"- 50° E. . 



6 



32 



38 



15 



8 



1 







0.5 



" 24. 



" 'i 110°-115° E. . 



9 



4 



21 



16 



12 



14 



12 



10 











1 



49 



44 



4 



1-5 



0.5 



" 25. 



75°- 83° E. . 



11 



2 



6 



6 



9 



21 



23 



21 



10 



8 



10 



13 



11 



17 



14 18 



" 25. 



25°- 30° E. . . . 



19 



9 



3 



3 



8 



30 



17 



11 



9 



24 



10 



9 



15 



23' S 2 



" 2l!. 



" " 25°- 30° E. . 



15 



8 



3 



5 



9 



19 



26 



15 



10 



10 



8 



7 



13 



22 21^ 9 



« 2G. 



" " 55°- 60° E. . 



16 



4 



3 



8 



13 



19 



25 



14 



10 



5 



3 



9 



11 



19,25 18 



" 2U. 



115°-120° E. . 



6 



5 



1 



1 



10 



20 



28 



21 



3 



6 



12 



12 



15 



19124' 8 



« 27. 



ia5°-120° E. . 



16 



4 







5 



15 



26 



18 



17 



9 



4 



2 



2 



7 



20 



34 21 



" 2'i. 



" " 45°- 60° E. . 



20 



10 



1 



1 



10 



14 



22 



23 



13 







1 



3 



12 



19 



20J25 



" 28. 



N. 40. Desolation Island 



10 



2 







1 







16 



32 



34 



-5 







2 







'' 



21 



40 15 



There seems not to be a great dift'erence between the limits of the N. E. trades 

 in the eastern and western part of the Indian Ocean at all equal to that in the 

 Atlantic. In Zone 25(30° to 35° S.) we see a certain predominance of S.AV. winds, 

 which in the southern hemisphere correspond to the N. W. in the northern. In the 

 North Atlantic Ocean there is a zone of prevailing northerly winds, rather N. W. 

 than N. E. Thus in the Indian Ocean, especially near the coast of Africa (25° to 

 30° E.) we are already out of the S. E. trade, while S. and S. W. are yet prevailing. 

 (See Plates 6, 6 and 7.) 



Between 35° and 40° S. the westerly winds prevail very largely, and further 

 south the number inci'eases. Besides the large percentage of winds from this 

 direction, they are also very strong, and in all respects prevail more extensively 

 than in the corresponding latitudes of the northern hemisphere. It will be seen 

 that the difference of pressure between north and south is here very great, the 

 pressure being very low in the Antarctic regions, and high at the S. limit of the S. E. 



