270 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



solar constant generally corresponds to a low number of sun spots, 

 and as a general result Dr. Abbot comes to the conclusion that an 

 increase of 25 sun spot numbers may be attended by i per cent 

 increase of solar radiation. If this be correct, Dr. Abbot finds that 

 as the average range of sun spot numbers in the 15 sun spot cycles 

 from the year 1750 to the year 1906 was 90, so we may expect that 

 an average sun spot maximum is attended with 3.6 per cent more 

 emission of solar radiation than the minimum of sun spot activity. 

 According to computations made by Dr. Abbot, this might be ex- 

 pected to be attended with a general increase of terrestrial tempera- 

 ture of 2.5° C. 



Dr. Abbot has also kindly sent us the measurements of the solar 

 constant made at Mount Wilson during the months June to October, 

 1916. The mean value of the solar constant was 1.955; the mean 

 relative number of sun spots that year was 50, which agrees well 

 with the value of the solar constant, according to Dr. Abbot's con- 

 clusions. 



DR. Clayton's investigations on correlation between solar 



RADIATION AND TERRESTRIAL TEMPERATURE 



Of special interest for our researches is the paper by Dr. H. Helm 

 Clayton, of Argentina, on the " effect of short-period varia- 

 tions of solar radiations on the earth's atmosphere," given us by 

 Dr. Abbot, in which the author definitely proves that there is an 

 intimate relation between the short-period variations in the solar 

 constant, as measured at Mount Wilson, and the variations of air 

 temperature at several meteorological stations at the earth's surface. 



By using the method of correlation, as worked out by Karl 

 Pearson, Dr. Clayton first makes a comparison between the changes 

 of the solar constant, as observed at Mount Wilson, and the changes 

 of temperature at Pilar in Argentina during the months July to 

 November, 1913, and the months from June to October, 1914. He 

 found that an increase of the solar constant was regularly followed 

 by an increase of the temperature at Pilar. The maximum cor- 

 relation follows one to two days after the corresponding solar values. 



By using the same method, Dr. Clayton also determined for 29 

 other stations, distributed over the globe, the correlation coefficients 

 connecting temperatures with solar constant values, obtained at 

 Mount Wilson in 1913 and 1914. He found that at some places 

 there was decided positive correlation, i. e. increase of temperature 

 follows increase of solar radiation, while at other places there was 



