C. EASTON, On Lockyer’s 35-year period in the solar activity. 
‘60 1780 1600 1820 1840 1860 
IT ian) T 
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Fig. 1 
M—m curve of the solar activity since 1760. 
Proceedings Royal Acad. Amsterdam. Vol. XI. 
Vern 7 
Curves of spot frequency in the 1l-year cycle 
since 1834, 
