166 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 19 3 8 



has plans for carrying out such a program of observations daily as 

 soon as funds may become available for the purpose. 



With 95 percent of the earth's atmosphere below the apparatus, 

 better measurements of the ultraviolet light could be made than at 

 any station on the earth's surface. Notable advances in the design 

 of apparatus for measuring the ultraviolet part of the solar spectrum 

 have recently been made by Dr. O'Brien of the University of Rochester. 

 Such apparatus yields photographic records by means of which a 

 quantitative estimate of the ozone content of the upper air can be 

 made daily with a high order of accuracy. The part which this ozone 

 plays in modifying the amount and character of sunshine at the 

 earth's surface is of very great importance. For weather and biologi- 

 cal behavior are undoubtedly sooner or later dependent upon both 

 the quantity of ozone and the quality of solar radiation received near 

 the surface of the earth. 



The idea that weather may be associated with changes in the sun- 

 spot cycle is not new. Many investigators have attempted to find 

 relationships between sunspots and weather changes with the ultimate 

 hope that since we can predict with reasonable accuracy the main 

 trends in the solar cycle we may ultimately be able to predict likewise 

 the main trends in changes of weather. The relationship between 

 weather and sunspots is not a simple one. While some may doubt 

 that any direct relationship holds at all, we might say frankly that 

 there is certainly no adequate proof to the contrary. 



In spite of many conflicting results, it appears that in general the 

 temperature of the world at large is somewhat higher at sunspot 

 minima than at sunspot maxima. This seems at first paradoxical 

 since we might well expect that at sunspot maxima the sun would 

 send us more heat and radiation than at sunspot minima. Many of 

 Dr. Abbot's observations, especially during the earlier years, seem to 

 corroborate this. Yet the surface temperature of the globe could be 

 actually cooler in years when the earth is receiving more heat from 

 the sun, for increased heat produces increased evaporation which in 

 turn generally results in increased rainfall. Increased rainfall actually 

 lowers the temperature of the earth's surface and again by evapora- 

 tion, continues to cool the air immediately above. Furthermore, with 

 the warming of the earth, a vast convectional system of atmospheric 

 currents results. As air warmed near the surface of the earth rises, 

 cold air flows in from the polar regions with its chilling effects. It 

 appears entirely possible that even with an increase in the heat received 

 by the earth from the sun, so far as surface conditions are concerned, 

 actually lower temperatures would occur at selected regions. 



One thing is certain, and that is that all the weather on the earth 

 is produced ultimately by the sun. So far as changes in the sun's 

 radiation affecting the general circulation of the atmosphere are con- 



