EEPOKT OF THE SECRETAEY. 



89 



centimeter per minute appears to attend an increased spottedness of 

 the sun represented by 100 Wolff sun-spot numbers. 



(h) Short interval irregula/r variability. 



The observations which had been begun in the year 1911 and con- 

 tinued in the year 1912 at Bassour, Algeria, simultaneously with 

 similar observations at Mount Wilson, CaL, were concluded in 

 September, 1912. The observations obtained at the two stations have 



now been completely reduced and compared. The results given in 

 the accompanying diagram show conclusively that if high values of 

 the solar radiation (outside the atmosphere) are found from Cali- 

 fornia observations, the values found fi'om Algerian observations 

 will be high also, and vice versa. In other words, the fluctuation of 

 the " solar-constant " values which had been found in California in 

 former years are now shown to be no local phenomenon due, per- 

 haps, to atmospheric disturbances, but rather a phenomenon which 

 is general over the earth's surface and which must be attributed to 

 causes outside the earth altogether. It would be conceivable that 

 such a cause might be the interposition of meteoric dust or other 

 matter between the earth and the sun; but other evidence, which is 

 more fully explained in Volume III of the Annals of the Astro- 



