MAGNETIC OBSERVATIONS 



297 



tiou, as also the approximate corresponding mean sun-spot frequencies according to Dr. Wolf 

 and Professor Wolfer,* are as follows : 



The references for each of the above series are as follows : 



Fort Conger, Grinnell Land International Polar Expedition to Lady Franklin Bay, Grin- 

 nell Land, by Lieut. A. W. Greely. (Volume 2, reduction of magnetic observations by C. A. 

 Schott.) Washington, 1888. 



*As collected and plotted by Mr. W. Ellis in his paper on the relation between diurnal range of magnetic 

 declination and horizontal force and solar spots (Proceedings of the Royal Society. Volume 63, pp. 64-78). 

 The values after 1896 are exterpolations based on Mr. Ellis' curves ; these are indicated by enclosure in paren- 

 theses. 



