(54) 



namely the mountain station Santis and St. Helena, which perhaps 

 is due to the peculiar situation of these stations. 



At St. Helena, where the windvector ought to turn with an 

 anticlockwise motion, (to the left) the veering is to tiie right, as if 

 St. Helena were situated in nordierly latitude. At this small latitude 

 (1(5° .Sj the windellipse is, as has been noticed above, very Hat so 

 that the veering of the wind is a rather uncertain factor. 



For the Dutch stations the theory api)ears to be so well in 

 accordance with the observation that the juirpose of this investigation, 

 namely determining the friction coefficient from the seinUUurnal 

 variation of wind and barometric height, and then, with the help 

 of this value, deducing the munodluriial gradient \ariation from the 

 corresponding wind variation, seems attainable. 



For such an in(|uiry the wind observations made during 25 

 consecutive years on board the lightship Tsrschellingerbank in the 

 North of the countiy, oiler an excellent material, and it is interesting 

 to investigate in what respect the gradient variation differs for two 

 places so differently situated as de Bilt and Terschellingerbank. 



5. Table H shows the diurnal \arialion of the wind for both places. 



TABLE II, diurnal variation of the Wind 

 in cm. p. sec, t ^0 =z Noon. 



de Bilt, N. Lat. 52T/, L. G. 5°11' hourly observations (1903— 1908). 



Winter v = 15.1 cos {nt — 260°) + 10.4 co.v (2 nt — 279°) 

 u = 11 .5 cos { lit— 17°) + 12.1 cos {2nt— 3 3°) 

 A = 24F A = 24(r 



Spring V = 71.4 cos {nt — 256") + 21.8 co^ (2 nt — 337°) 



i( = 52.7 cos { nt— 14°) + 2L8 cos (2 nt — 74°) 



A = 242° A = 263° 



Summer v = 95.6 cos {nt — 261°) -f 27.7 cos (2 nt — 358°) 

 u = 86.1 cos {nt— 25°) + 22.5 cos (2 ?it - 79°) 

 A = 236 A = 279° 



Autumn v = 40.7 cos {nt — 264°) + 14.9 cos (2 nt — 316°) 

 u ^ 30.3 cos {nt— 19° ^ 4- 16.2 c06- {2nt— 56°) 

 A = 245° A = 260° 



Year v = 55.6 cos {nt — 260°) + 1 6.8 cos (2 nt — 333°) 

 u = 45.0 cos {lit— 21°) -f 17.4 cos {;lnt— 65°) 

 A = 239° A z= 268° 



