30 Arotowshi — Pleionian Cycle of Climatic Fluctuations. 



Well-pronounced minima preceding by approximately 12 

 rotations (or more or less 9 months) those of spots ; less pro- 

 nounced minima coinciding or preceding by a few rotations 

 the maxima of sunspots ; then, in each 11 years' cycle, another 

 minimum between the minimum and maximum of the curve 

 of sunspots and two minima between the maximum and the 

 following minimum. And so, in the period of more or less 

 11 years' duration there are 5 maxima of the ratio of faculae 

 and umbrae; the first coincides with, or closely follows the 

 minimum of spots, the second occurs between the minimum 

 and the maximum and the three others occur between the 

 maximum and the minimum of the sunspot curve. 



It may be useful to mention that the range of these varia- 

 tions is well pronounced. The highest observed ratio of 10 

 consecutive rotations is 73-74, while the lowest figure is 2 - 42. 

 But these are extreme values. The average ratio of the 15 ob- 

 served crests is 26*93 and the mean of the corresponding de- 

 pressions is 11 - 47, or less than one-half. Such are the facts. 



To come back to hypothetical considerations, it may be 

 asked how these fluctuations of the ratio of faculae and sun- 

 spots can be explained? 



Let us say that the depth to which our terrestrial storms ex- 

 tend is limited by the surface of the earth crust or the surface 

 of the sea. Evidently the sun does not present similar condi- 

 tions and d priori we may admit the possibility of variations 

 in the depth to which the circulation of the solar atmosphere 

 may extend. If so, the proportion of faculae to spots must 

 vary, and when the faculae are more predominant, we may sup- 

 pose that the ascending columns of vapors come from greater 

 depths and that, in consequence, the radiation is increased. 

 Some sort of tidal movements making the solar atmosphere 

 more or less expanded would explain the possibility of changes 

 of depth to which the vertical circulation extends. 



Now, since the maxima of solar faculae-umbrae ratios reoccur 

 — just like the terrestrial thermo-pleions, ombro-, helio- and 

 baro-pleions, — at intervals of 2 to 3 years, and since some 

 striking time coincidences exist, I shall call these maxima 

 of solar fluctuations, horme-pleions, — which simply means 

 pleionian impulses. 



I say expressly horme- and not arche-pleions, because this 

 last name must be reserved for the solar, or planetary, or 

 cosmical relations which cause the changes of the solar atmos- 

 pheric vertical circulation, changes for which the horme- 

 pleions are simply numerical expressions. 



In the foregoing considerations I have spoken of solar clouds. 

 This expression may displease some of the students of solar 

 phenomena. But what difference does it make if condensation 



