12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



Other side. During periods of high maxima of solar activity the pres- 

 sure is low at Cape Town, whereas with moderate maxima of solar 

 activity the pressure is high at Cape Town, just as it is at New York 

 and Marseille in the Northern Hemisphere. At Laurie Island, 6i° S. 

 shown by the broken line, the pressure was high with high solar activity 

 in 1917 and low with moderate solar activity in 1905-6 and 1928, just 

 as it was at Upernivik and Yakutsk in high latitudes in the Northern 

 Hemisphere. The observations at Laurie Island now cover two sun- 

 spot periods, and great credit is due the Argentine Government for 

 maintaining this station with great difficulty and with much expense 

 in this high southern latitude. It is hoped that in the coming years 

 other nations may find it possible to maintain a net of stations in 

 high southern latitudes. 



An effort was made to map the j^sitions of the centers of action 

 at different sun-spot epochs. For this purpose the data published in 

 World Weather Records (Smithsonian Misc. Coll., vols. 79 and 90) 

 were used. These volumes contain the most complete set of data 

 available, but for vast areas of the world there are still no observations, 

 and for this reason any map of world conditions must be incomplete. 



Five-year means of pressure, with the central year the epoch of 

 maximum sun spots, were obtained for all available stations and plot- 

 ted on a world chart. Lines of equal departure from normal were 

 drawn for each 0.3 mm in the Tropics and for larger intervals in 

 higher latitudes. The areas where the pressure was above normal 

 are shaded. These areas for three epochs of maximum sun spots are 

 shown in figure 10. The epochs are arranged in the order of intensity 

 of solar activity as indicated by the number of spots, 191 5-19, 1891-95, 

 1904-8. (See table 2.) The data were insufficient for earlier epochs. 



During the marked maximum of spots 191 5-19 the pressures are 

 shown very high in high latitudes in both the Northern and Southern 

 Hemispheres, with centers of greatest departure over Greenland and 

 northern Siberia in the Northern Hemisphere and secondary centers 

 over the cold waters off the coast of Africa and of Lower California. 

 In the equatorial belt and over the warm waters of the Gulf Stream 

 and the Kuro Siva the pressures were generally below normal, with 

 centers of low pressure over the North Atlantic and North Pacific 

 between 40° and 50° N. Corresponding centers of low pressure are 

 shown in the Southern Hemisphere between 30° and 40° S. With 

 a lessened intensity of solar activity in 1891-95 the centers in high 

 latitudes appear displaced toward the Equator, with the exception of 

 a low-pressure area over northern Europe. The center of high pres- 

 sure over Greenland has moved southward toward Hudson Bay. and 



