ON “QUIET” DAYS DUKING THE ELEVEN YEAIiS 1890 TO 1900, ETC. 
487 
this point, i)iit has detectod no certain lau'. It is, howevei', oijen to doiiht wliethei' 
a short lag—a month or two for instance—would with certainty lie sliown l)y the 
method he employed. 
Before concluding, I wish to acknowledge the valuable assistance given me hy 
several members of the staff of the Observatory Department of the National Physical 
Lahoratoi'y. 
Mr. 1. yV . Baker, the Chief Assistant, gave much useful help in the Interpretation 
of the earlier magnetic records. 
To Mr. G. Badderly and Mr. B. Francis I am indebted for mnch careful 
arithmetical work, especially in coiiiiection with the calculation of Fourier coefficients. 
1 he calculation work lias lieeii exceedingly heavy, and some ei'rois have doiilitless 
escaped me, but every reasonable precaution has been taken to secure acciimcy. 
