According to the expectation formulated in § 1, by this improved 

 method a smaller minimum value is found for the angle of deviation 

 than in table 1; at the same time the positions of the maxima and 

 minima are somewhat shifted. 



It may he noticed that for the coirelation lietween Municii and 

 JiCrwick for pressure dif/'crcnrcs sx negative value, r,,^^ — 0.491 

 has been found of the same order of magnitude as the /wWwi/ corre- 

 lation of deviations from pressure between Clermont and Christiansund 

 viz. — 0.536, and between the I'egion of the Azores and Iceland. 



The laborious calculations of partial corr. coetF. may, therefore, 

 .iften be avoided by forming (lili'i'ri'iicea, by which process large 

 common influences are eliminated. 



3. For a third investigation the average wind for the Nether- 

 lands has been calcidaled (for the same period as mentioned in § 2 

 and 7 a.m.) from the stations De Bilt, Flushing, Helder, and Groningen 

 and this average wind has been associated with pressure differences 

 between De Hilt on the one hand and Sylt, Dresden, Miilhausen, 

 lie d'Aix, Valencia, and Lerwick on the other hand; the azimuths 

 of these stations differ about (ïO° V. 



The ranknumbers, average values and standard deviations now 

 become ; 



22 

 Proceedings Royal Acai). Amsterdam. Vol. XVIII. 



