l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 68 



centers of the continental and oceanic masses. There is one center 

 oscillating around the center of South America, another around the 

 center of North America, and another around the center of Africa. 



The changes in the other centers are more difficult to determine, 

 but there appears to have been a maximum which moved from 

 southern Greenland up to Jacobshavn, and back again to St. Johns 

 New Brunswick, a minimum which moved from Jurjew, Russia, to 

 Stykkisholm, and back again to northern Europe, and a maximum in 

 the South Atlantic which moved from South Georgia to Laurie Island. 

 There were also indications of a minimum which moved from the 

 Central Atlantic to the coast of Spain during October, and another 

 which moved from the Central Pacific to the coast of Chile at the 

 same time. There were no doubt other centers in Siberia, Australia, 

 the Indian ocean, the South Atlantic and Pacific oceans. An ex- 

 tremely interesting point is that all those centers, whose motion could 

 be approximately determined, oscillated in the anticlockwise manner 

 in both hemispheres, reached their most northern point in October, 

 and the most southerly in September and November with one or two 

 exceptions. » 



This movement of centers of oscillation is very similar to a phe- 

 nomenon of the same kind found some years ago in the United States 

 when studying temperature oscillations of about two years' corre- 

 sponding no doubt with oscillation in solar radiation of longer period. 

 (American Meteorological Journal, Vol. 2, p. 126, Detroit, 1885.) 

 I am led to infer that an oscillation in the areas of positive and nega- 

 tive departures is characteristic of all effects of solar changes on the 

 earth's atmosphere and has been one of the reasons why the relation 

 between atmospheric phenomena has been difficult to detect, and why 

 periodic changes of all kinds have been masked. 



FERIODIC CHANGES IN SOLAR RADIATION AND IN THE 

 TEMPERATURE AT BUENOS AIRES 



• 



An interesting line of inquiry is in regard to whether any periodicity 

 can be detected in the changes in solar radiation. Many years ago. 

 Prof. Balfour Stewart used a method of seeking hidden periodicities 

 by means of averages of periods of successively greater length. 

 Prof. Arthur Schuster gave a greater refinement to this method by 

 the use of harmonic analysis and the construction of a periodgram. 

 This method assumes that there are fixed periods to be discovered, 

 but there is a possibility of a kind of periodicity without a fixed epoch. 

 For example the spots on the sun reappear near the same part of the 



