194 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'JO 



Gates that the two-year period plays no great part in the conditions 

 at Batavia. Taking the intervals in months, for example between 

 the maxima in a long series of years in the different curves, one 

 finds an average interval between them of 32 to 33 months, which 

 corresponds to a quarter of a sun spot period. 



Comparing these curves for meteorological relations with the 

 sun spot curve (S) which stands lowest in the figure, we see as a 

 rule that at minimum of sun spots a maximum of air pressure, 

 temperature and of daily temperature amplitude occurs and the 



Figure 69. Batavia. Curves show successive three-year means of tempera- 

 ture, (T) ; air pressure, (B) ; rainfall, (P) ; sun spots, (S) ; prominences, 

 (RC) ; according to the observations in Rome up to 1898, and in Catania. 



minimum of cloudiness and precipitation. At maximum of sun 

 spots there occur on the whole similar but secondary maxima and 

 minima in agreement with the above mentioned quartering of sun 

 spot periods. The short periods of about three years agree partially 

 with corresponding periods in the prominence curves R, P and C. 

 We shall speak later of this again. 



The correspondence between variations in the sun spots and in the 

 temperature and air pressure in Batavia is particularly well seen 

 if one takes the' separate yearly means of meteorogical elements by 

 consecutive three-year intervals. The result of such a computa- 

 tion is given in figure 69, where the curves of air pressure and 

 temperature are given with increasing scale numbers upwards and 

 the curve of sun spots with increasing scale numbers downwards. 

 The eleven-year period of meteorological phenomena comes very 

 plainly to view, but it is to be noted that there are indications of a 



