Magnetic Declination and Horizontal Force and Solar Spots. 67 



rather than endeavour to make reduction from one to the other for a 

 portion of the series. 



Examination of the collected curves will, I think, show that the 

 extension of the period previously employed by inclusion of the new 

 resnlts, extending from 1878 to 1896, has produced carves that offer 

 striking points of interest. Selecting the extreme points of the 

 several curves, or, which is better, taking the successive least and 

 greatest values from Table II, and from the corresponding table 

 of the previous paper, for magnetic values, and from Table III, and 

 from the corresponding table in vol. 43 of the ' Royal Astronomical 

 Society Memoirs,' for smoothed sun-spot values, the following epochs 

 of minimum and maximum are obtained : 



Table of Epochs of Magnetic and Sun-spot Minima and Maxima. 



The mean magnetic epoch is taken to be the mean of those for 

 declination and horizontal force. These vary somewhat for the 

 epochs Nos. 1 and 3, but the mean epoch in both cases falls near to 

 the sun-spot epoch. 



Taking the differences between successive epochs of minimum and 

 maximum 1 2, 2 3, &c., the following intervals are found : 



