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ANNALS NEW YORK ACADEMY OF SCIENCES 



the pleionian center (Fig. 51) and expresses simply the tendency of the 

 displacements, during the years 1900-1909, and may serve as an illustra- 

 tion facilitating the comprehension of the problem. For precision it 

 would have been necessary to have detailed consecutive maps. 



The principal problem is of 

 course, what keeps the pendula- 

 li(»ii going? Without some exte- 

 ii(ir impulse, the movement would 

 (lie nut or could not even origi- 

 nate. It seems to me highly im- 

 ])robable that a mechanical work- 

 ing as is exhibited on the diagram 

 could be due to variations of the 

 Athintic ice conditions. Without 

 doubt, it is the cause of the for- 

 mation of pleions wliicli, repeating itself more or less periodically, gives 

 the impulse to the clockwork. 



The Russian pleions have shown some correlations with the equatorial 

 variation of temperature, illustrated by the consecutive cun^e of Arequipa. 

 The consecutive curve of New York also belongs to the i\.requipa type. 

 We see now how the tendency of the pleions to maintain their existence 

 complicates the problem of their mode of formation or origin. 



The following diagram (Fig. 52), which expresses graphically the last 



Fig. 51. — I'leionian pcndulations 



Fig. .'J2. — Pleionian amplitudes and the Arequipa curve 



problem I have to mention m connection witli the study of consecutive 

 maps, shows plainly that, independently of the pendulations, the Are- 



