1904.] Short-Period Atmospheric Pressure Variation. 



Types — continued. 



465 



Months in which types are 

 most conspicuous. 



Source of data. 



General remarks. 



Oct. — Apr. 



Sept.— Feb. 

 Oct.— Mar. 



Jan.— June 

 Oct.— Mar. 



Apr. — Sept. 



Oct. — Mar. 

 Apr. — Sept. 



Low press. 



High press. 

 High press. 



High pres3. 



Low press. 



High press. 

 Low press. 



Annales de l'Obsy. do Infante 

 D. Luiz 



Besume de las Obs. Met. de 



Provinces (Spanish) 

 Annales de l'Obsy. Cent. Phys. 



de Kusse 



55 55 



Kong. Sv. Yet. Ak. Handlingar, 



vol. 29, No. 3 



Meteorological Office 



Annales de l'Obsy. Cent. Phys. 



de Russe 



Meteorological Office 



Annales de l'Obs. Cent. Phys. 

 de Russe 



Kong. Sv.Yet. Ak. Handlingar, 

 vol. 29, No. 3 



Met. Zeitschrift, 1S86, and 

 Observations made at Hong- 

 Kong Observatory 



Met. Zeitschrift, 1899 



Report of Cent. Met. Obsy. of 

 Japan. 



Prominent in yearly curve. 



1886 no record. 



Yearly curve alone examined. 



Break in record 1875—1887. 

 Yearly curve alone ex- 

 amined. 



Yearly curve alone examined. 



Prominent in yearly curve. 



Short record. Prominent in 



yearly curve. 

 Yisible in yearly curve. 



All the curves for the half- 

 yearly and yearly values 

 show similar variations. 



light and which plays most probably an important role with regard to 

 the pressure variations at places which exhibit a mixed type of 

 pressure. The earth's surface as has been shown may be divided 

 mainly into two regions, one portion showing excess pressures at 

 certain epochs, while the other shows deficient pressure at the same 

 epochs. If the former region exhibits a greater excess than usual (as 

 an example, the Indian region in 1877), then the region over which 

 this type of pressure occurs may probably be more extensive, and the 

 boundary dividing the two chief types of pressure will necessarily be 

 pushed away from this region. Stations, therefore, that were just 

 on the fringe of this boundary may at these epochs become enveloped 

 in this more extensive high-pressure area, and will exhibit the Indian 

 type of pressure variation. 



Should the Cordoba region become more extensive than usual owing 

 to a similar cause, then the border stations will assume the Cordoba 

 type of pressure variation. It is not proposed to enter here into 

 detail on this point, as the subject requires very close examination, but 



