•_' s Arotowskir—Pleiohian Ci/cf<; of CI inn/tic Fluctuations. 



In order to investigate these phenomena more thoroughly, 

 the monthly means of temperature, atmospheric pressure, 

 rainfall, sunshine duration and thunderstorm frequency have 

 been taken into consideration and the changes from one year 

 to another have been studied by the method of overlapping 

 means. 



Among other results it was found that at many stations, par- 

 ticularly in equatorial regions, temperature rises or falls prac- 

 tically simultaneously and that the pleions disappear and 

 reappear more or less periodically at intervals of 2 to 3 years.* 

 The records of the Harvard Observatory station at Arequipa, 

 in Peru, have been taken as a standard of the occurring plei- 

 onian fluctuations,f and the results of the comparisons made 

 induced me to search for the cause of this cycle of climatic' 

 variations. 



After it was demonstrated that the cause of the formation 

 of pleions could not be attributed to the presence or absence 

 of volcanic dust-veils in the higher levels of the atmosphere,^: 

 it was but natural to search for their origin in the variations of 

 the solar atmosphere. 



It seems obvious that, if changes in the vertical circulation 

 of the incandescent solar clouds exist, these changes must pro- 

 duce oscillations of the quantity of thermal energy radiated 

 into space. 



A few words of explanation are necessary. 



Although it is difficult to imagine how the heat of the solar 

 atmosphere originates, or where it originates, we must admit 

 that the amount of heat is greater below the incandescent pho- 

 tospheric clouds than above, — simply because these clouds are 

 a phenomenon of condensation, due to loss of heat, and because 

 condensation could not take place if the temperature below the 

 clouds was not higher than the temperature above. In conse- 

 quence, we must admit that, just as in the case of terrestrial 

 atmospheric conditions, the radiation into space, from below, 

 must be a question of cloudiness. This radiation is not neces- 

 sarily constant. If the vertical currents producing the ascend- 

 ing clouds are intensified, the loss of heat must be greater. 

 For the sake of comparison, our terrestrial Cu-Ni clouds, 

 with their panaches of false-cirri, may serve as an example. 



I imagined that the solar-faculse, which always accompany 

 the formation of sunspots, might have an origin similar to the 

 false-cirri, and this vague aualogy led to the supposition that 

 perhaps the facnlse would give some information concerning 

 possible changes of the intensity of the output of solar energy. 



* Annals N. Y. Acad. So., v. xxiv, p. 39, 1914. 

 f Bull. Am. Geogr. Soc, v. xliv, p. 598, 1912. 

 % Annals N. Y. Acad. Sc, v. xxvi, p. 149, 1915. 



