1320 



the bottom of the atmosphere is in at'cordance with isobars and 

 rotational intiuence. It is shown by Braak's isobaric chart how the 

 NE-trade, delineated on it after van der Stok's results, deviates to 

 the right in the norlliern hemisphere, has no deviation at all at the 

 equator (being directed perpendicularly to the isobar), and deviates 

 to the left in the southern hemisphere, having turned eventually to 

 a northwesterly direction. 



Above Batavia however, already at a height of ± 2 km., the 

 wind deviates to the SW, blowing pretty parallel to the isobars, as 

 1 could judge from the isobaric chart projected for that level. There 

 the aircuirent does not proceed from the northern hemisphere, but 

 from the part of the ocean which lies to the SW of Java. 

 ' The motion of the air parallel to the isobar points to a stationary 

 character of the current, wMiich evidently cannot develop in the 

 bottomlayers, owing to disturbances caused by friction (cf. Hann's 

 Lehrbuch der Met: 1915, p. 437). 



The pressure-gradients which maintain the westmonsoon must 

 change signs at a certain height, because the influence of the tem- 

 perature-gradient on them grows in excess of that of air-pressure- 

 gradients, the two gradients having contrary signs. 



Quite in accordance with this we see the Westmonsoon disap- 

 pearing at a height of a few kilometers, and we meet easterly 

 winds above that level. 



The isobaric charts for the different levels not being reliable, 

 I give here only the pressure-differences up to 9 km. between 



Pressure-difference for Jan. — Febr. 



Height 



Batavia-Port 

 Darwin 



Batavia-Koepang 



