308 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. "/O 



cal method of correlation, which though somewhat tedious, gave 

 results wholly free from personal bias. The method answered the 

 question: Does a coincidence of departures from normal tempera- 

 tures, indicating a common cause, appear from the records of the 

 investigated stations? His method did not indicate for non-periodic 

 changes, when such changes took place, or how great their mag- 

 nitudes. 



Some of the conclusions from these two investigations were as 

 follows : 



Smithsonian Newcomb 



1. Higher temperatures prevail at i. Higher temperatures prevail at 

 sun spot minimum. sun spot minimum. 



2. An increase of lOO Wolf, num- 2. Average sun spot maxima since 

 bers is attended by about 1° C. de- 1840 have been attended by about 

 crease ot temperature. 0-26 decrease of temperature. 



3. Indications of wide-spread coin- 3. " Apart from this regular fluctua- 

 cidental short interval temperature tion with the solar spots, and this pos- 

 fluctuations, reasonably attributable sible more or less irregular fluctua- 

 to solar variations, are found, but not tion in a period of a few years, the 

 without conflicting evidence. sun's radiation is subject to no change 



sufficient to produce any measurable 

 effect upon terrestrial temperatures." 



Since these results were published, short interval irregular solar 

 variation of several per cent range has been established. The vari- 

 ability of the sun is now confirmed^ by (a) Mount Wilson, Cali- 

 fornia, observations of the " solar constant," (b) comparison of 

 Mount Wilson and Bassour, Algeria, observations, (c) comparison 

 of Mount Wilson and Arequipa, Peru, observations, (d) compari- 

 son of Mount Wilson and magnetic observations, (e) comparison 

 of Mount Wilson " solar-constant " work with Mount Wilson 

 " solar-contrast " work. The cumulative effect of this evidence is 

 overwhelming. Besides this it has been shown by H. H. Clayton 

 that correlations exist between fluctuations of solar radiation and 

 changes of terrestrial temperature and pressure. These correla- 

 tions are positive for some stations, but negative for others, and 

 almost lacking at still others. This explains at once why such inves- 

 tigations as those we have been discussing could not with certainty 

 exhibit strong evidences of short interval solar variability. Owing 

 to complexities not yet understood, brief intervals of higher solar 



* See Annals of the Smithsonian Astrophysical Observatory, 3 ; Smith- 

 sonian Miscellaneous Collections, 65, Nos. 4 and 9; and 66, No. 5; Terrestrial 

 Magnetism and Atmospheric Electricity, 20, 143, 1915. 



* Smithsonian Misc. Coll. Vol. 68, No. 3, 1917. 



