264 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



POSSIBLE ONE-YEAR PERIOD IN THE SUN SPOTS 



It is yet clearer that apparently there is also a period of one year 

 in the variation of the sun spots. Curve II of figure 96 shows a 

 very distinct one-year period. This curve is the result of a consecu- 

 tive eight-monthly smoothing of the differences which are given in 

 curve I as above stated. The one-year period is particularly well 

 shown in the interval 1890 to 1895. It is, however, possible that this 

 period is accidental and results from the incompleteness of the obser- 

 vations. In the years 1890 to 1895 there exists a minimum for this 

 curve in midwinter, or exactly at that time of year when the observa- 

 tions of sun spots at Zurich are on the whole least complete. 



VARIOUS PERIODS 



We have earlier remarked that in several meteorological elements, 

 for example at Batavia, there appears to be a period whose average 

 length is 32 to 33 months. That is about two and three-quarters 

 years. This apparent period, like the eleven-year period, is subject 

 to differences of length and ranges between two years and three or 

 even four years. It is questionable whether this period depends 

 upon a combination of several elementary periods which perhaps 

 may be associated with corresponding periods on the sun. We have 

 already remarked that a two-year sun spot period seems to be recog- 

 nizable and we have also noted that it was found by the two Lockyers 

 that there is a period in the solar activity of about 3.7 years. They 

 find it both in the prominences and in the variations of the spectro- 

 scopic lines of the sun spots, as also in the heliographic latitude of 

 the sun spots. Such a period in the solar activity of three to four 

 years appears also in several of our curves. If, however, the sun 

 spot periods of two years and between three and four years make 

 themselves felt in the meteorological phenomena we could obtain 

 from this a fairly close relation with different time intervals, of 

 which, however, the average duration may very well be about two 

 and three-fourths years. 



SECULAR VARIATIONS IN SOLAR ACTIVITY AND IN METEOROLOGICAL 



RELATIONS 



We have not treated of the very long period or secular variations 

 but yet we will mention some peculiarities in several of our curves 

 which are of interest in connection with the question of long periods. 

 Many of our graphical representations show the relations between 



