1317 



October, reaching 21 — 22 km., it descends in the southern snmniei' 

 to 18 — 19 km. and afterwards soon goes down to ihe level of 

 12—13 km. in the month of June. 



The velocity of this n[)|)ertrade is comparatively small, taking into 

 account tiie great altitude at which it blows; however in levels 

 exceeding ± 24 km. its main velocity increases and it changes into the: 



Krakatoa-ujind, as was called by me the ecpiatorial Eastwind 

 which blows at a height of about 30 km. with a velocity of 

 db 40 m. p. sec. 



This current which manifested itself in the days following on the 

 eruption of Krakatoa, was twice found back al Batavia, once in 

 March and once in Septend)er. 



High Westwifids. Between the layeis of the uppertrade in the 

 southern winter is driven like a wedge a lajer of high westerly 

 winds. The lower limit of these winds reaches lowest in June, 

 descending to 16 — 17 km.; the upper bmit however is unceilain 

 owing to scarcity of observations; presumably it ascends to a height 

 of ± 24 km. in the same month of June. 



The velocity of these high westerly winds may be said to be 

 relative!}' small for the high altitude of their region, but each time 

 in their season when a balloon entered that region they were niet 

 with and they were found to be uninterrupted by westerly winds. 



For the rest these winds mostly have a southern component. 



Explanation of the system of aircurrents. 



To give a satisfactory explanation of the system of aircurrents 

 described above is as yet hardly feasible, as the Batavian observa- 

 tions are the only ones in the austi-alasiatic pait of the equatorial 

 and subtropical zones. So the attempt to explain them as made here 

 has to be based partly on conjecture. 



In order to make an endeavour to investigate the relation between 

 the system of aircurrents on one side and pressure together with 

 temperature on the other, in the first place monthly values of 

 airpressure have been calculated for kilometer levels up to 26 km. 

 making use of the results obtained with registering balloons, including 

 those for humidity. ') 



In doing this, for the height and temperature at tlie base of the 

 stratosphere the following values vveie taken. 



M Observat. Batavia, Verhandelingen N". 4. 



