2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



and of fall in the solar constant of radiation appeared to be indicated 

 by Smithsonian observations. These apparently averaged 0.7 percent 

 of the solar constant in amplitude. They appeared to be followed by 

 regular patterns of change in the march of terrestrial temperatures. 

 Figure i shows such a result. Such temperature changes were op- 



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V^ -/*' ys- 

 -sii-lei ^fz 



Fig. I. — Comparison of mean march for 25 days of departures from normal 

 temperature at Washington in February, associated (dotted curves) with ups 

 and downs of the solar constant of radiation and (full curves) ups and downs 

 of critical frequencies of ionization for the layer Fe. Solar change on zero day. 



posite for rising and falling solar changes. They appeared to persist 

 for at least 17 days, and were of the order of 10° F. No regularity 

 was then discovered in the intervals between the observed solar 

 changes, but this could have been due to the lack of many days of 

 observation. Even at the best stations, clouds and accidental errors 

 prevent continuous daily measurements of small changes of solar emis- 

 sion of radiation. Indeed meteorologists, physicists, and astronomers, 

 with few exceptions, have remained to this day skeptical as to whether 

 the Smithsonian observations of the solar constant really discover 

 solar variations from day to day. They are inclined to attribute the 

 apparent solar changes to unavoidable error. 



