l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



largest pressure difference occurs at Winnipeg on zero day, at 

 Chicago on the second day, and at New York on the third day after 

 the solar constant event. 



It is, of course, to be expected that any wave of disturbance of 

 barometric pressure appearing in winter at Winnipeg on a certain 

 day would drift eastward, and appear at Chicago and New York after 

 about the intervals of time here shown. This is only ordinar\- well- 

 knovv^n meteorological experience, and proves nothing as to the influ- 

 ence of solar variation. But that in the mean results of such numerous 

 groups of cases there should remain residuals of the order of 0.15 

 inch in barometric pressure, and residuals so well exhibiting the 

 l^rincipals of continuity and proportionality relative to a supposed 

 cause seems to- be, at least, very harmonious to the hypothesis that 

 the assumed cause, solar variation, has a real relationship to the 

 observed effects. 



As it has been suggested to me that these results of Clayton's 

 would perhaps be essentially modified had he been advised of the 

 corrections to scale, mentioned in connection with table 2, I may add 

 that his results concern only solar constant observations of the winter 

 half-years between October i, 1918, and March 31, 1922, during 

 which only the few values of October, 1921, would be apprecia1>ly 

 affected by the new changes of scale. It will appear, too, by inspection 

 of figure 3, that this period was one of unusual freedom from great 

 swings of the solar constant such as we attribute to general changes 

 of the solar surface temperature, so that the fluctuations which he 

 discusses will have been principally those of short interval. 



From the various evidences assembled in this paper, added to many 

 others previously published, my colleagues and myself are more and 

 more encouraged to believe that our long investigation of solar varia- 

 tion will yield useful positive results. 



