126 



sions from a small coral island in the Java Sea (one most north 

 of the Duizend-Eilanden ') ; moreover he erected an anemograph 

 (recording velocity and direction) on the neighbouring Noordwachter 

 light house (50 m. above sea level). These balloon observations are 

 still in hand, but of the wind records the results of a few months 

 are available. 



These, however, have shown that there also, i. e. at a distance 

 of no less than 68 km. from the Sumatra coast, still considerable 

 land and sea breezes, are found and, seeing that the islet whence 

 the balloons were sent up is situated respectively 60 km and 70 km 

 from the Java and Sumatra coasts, the results there obtained will 

 neither be free from the effect of land and sea breezes "). 



We trust to obtain and publish in due course the various results 

 for land and sea breezes and Espy-Köppen effect, to be deduced 

 from the foregoing observations, after the necessary reductions have 

 been completed. 



For the present we will deal with the results for the asmospheric 

 layers above 4 km only. 



Then it will at once appear from the graphs that the amplitude 

 of the diurnal variation must be a minute one for both components, 

 in any case too slight to be deduced with any certainty at all from 

 the results obtained. 



The semi-diurnal variation of the N. component is also a minute 

 one, however, the scattering of the points of observation is much 

 less and the curve drawn between these points deserves more 

 confidence. 



On the other hand, the amplitudes for the East component are 

 much larger, whilst the scattering of the points is also slight. 



According to this scattering one would expect mean errors of the 



') The expenses for this inve.'^tigation have for the greater part been covered 

 by funds put at the disposal of the Director of the K. Magn et Met. Observato- 

 rium on the occasion of the dissolution of the Nederl ind. Yer. voor Luchtvaart 

 (Netlierlands Indian Association for Aeronautics) with the purpose that these funds 

 should be utilised for such aerological researches. 



2) According to the observations on Noordwachter during July — November 1916 

 the amplitudes of the diurnal variation of the E-W and N-S compenents are res- 

 pectively 83 cm and 54 cm and, therefore are actually in inverse proportion to 

 the distances to the Sumatra and Java coasts of respectively 68 km and 100 km 



54 65 . . , 



seeing that — = t^. The phases are respectively 249° and 204°, agreemg with 

 8o 1 00 4 



. the phase of the N. component above Batavia at 0.1 km i. e. 222°. 



