135 



This consideration and the support, afforded by the phase pre- 

 viouslj arrived at for the Ci-drift, therefore leads to the following 

 conclusion : "Possible but not probable" by which is indicated at 

 the same time the manner to arrive at a better insight, viz. more 

 observations. 



The ascensions made on the Java-sea, which supplied a number 

 of observations up to about 11 km., have partij m.et the above 

 requirement, and may conceivably be taken as valid for Batavia. 



On the other part it has been decided to commence further ascens- ' 

 ions; these are now taking place during the change of the monsoon, 

 when the velocity of the wind (the non-periodical one) as well as 

 accidental errors ^) will be slight. 



SUMMARY. 



1. With a purpose of investigating the diurnal and semi-diurnal 

 oscillation of the motion of the air in the free atmosphere up to 

 high levels, a great number of pilot balloon ascensions took place 

 at Batavia during various hours of the whole day. 



2. For the first time some series of nocturnal ascensions of bal- 

 loons carrying lights, were then performed up to great heights, 

 following the device indicated by C. H. Leu ^) and as realized by 

 him in some cases. 



3. Afterwards will be published the various results for the lower 

 layers of the atmosphere up to 4 km. 



4. As regards the upper layers up to 10 km., it appears that the 

 material of observations is insufHicien^ for deducing a diurnal oscillat- 

 ion, on the other hand that for the semi-diurnal one leads up to 

 positive results. 



5. The amplitude of the semi-diurnal oscillation is larger for the 

 East than for the North component, the phase of which remains 

 uncertain. 



6. In the lower layers the amplitude and phase seem to be in 

 accordance with the theoretical results of Gold (Gold does not deal 

 with the upper layers in that respect). 



7. Up to 4 km. the phase of the semi-diurnal oscillation of the 

 East component diminishes, in this respect following the corresponding 

 phase of the oscillation of the air pressure. 



8. Above 4 km. it is obviously probable that the phase again 

 increases, thus effecting an inversion at a height of about 10 km. 



1) Circumstances have prevented till now (May 1st) from doing so. 



2) Quart. Journal. R. Meteor. Soc. 1909. 



