122 



ANNUAL. REPORT SMITHSONIAN INSTITUTION, 19 31 



days represented are unsatisfactory. It is indeed almost beyond the 

 limit of possible accuracy to observe the solar constant day after day 

 with such exactness that the differences between the absolute values 

 shall always evaluate changes correctly if reaching one-third of 1 per 

 cent or more. This is what is needed. We have in mind a few 

 improvements which may bring us to this degree of accuracy at 

 Montezuma, but unless other stations superior to Table Mountain 

 and Brukkaros are found it seems doubtful if fully satisfactory 

 daily values are obtainable to supplement the Montezuma record. 



FlOUKB 4. 



-Washington nnd Willlston temperatures associated with solar periodicities. 

 Five-month consecutive means 



Further studies made during the year tend to confirm the impres- 

 sion stated in last year's report that temperatures and barometric 

 pressures in the United States respond by opposite trends to positive 

 and negative sequences of change in daily solar-radiation values. As 

 yet, however, the evidence is not fully satisfactory owing to the 

 imperfection of the daily record of solar changes, as just explained. 



To promote statistical studies along these lines, a new instrument 

 designed to discover and evaluate periodicities in solar and weather 

 records has been designed. Its construction was aided by a grant of 



