Appendix. 101 



nected with the generation of electro-mag- 

 netic currents." HUMBOLDT. 



"A large proportion of winter heat of the 

 poles comes through the equatorial current." 



-YOUMANS. 



Aurora 



9. (Page 44.) " HOOD heard a noise as of 

 quickly moved musket-balls, and a slight 

 crackling sound during an aurora. He also 

 noticed the same noise on the following day." 



" FATHER PERRY of the Stonyhurst Ob- 

 servatory remarked that the green spectro- 

 scopic line characteristic of the aurora, could 

 be detected even where the unassisted eye 

 failed to notice any trace of light." 



"The fleecy clouds seen in Iceland by 

 THIENEMANN, and which he considered to be 

 the northern light, have been seen in recent 

 times by FRANKLIN and RICHARDSON, near the 

 American north pole, and by ADMIRAL WRAN- 

 GEL on the Siberian coast. All remarked 

 that the aurora flashed forth in the most vivid 

 beams when masses of cirrus strata were 

 hovering in the upper regions of the air, and 

 when these were so thin that their presence 

 could only be recognized by the formation of 

 a halo around the moon." 



