8. ([Page 42.]) "It cannot be doubted that electro-magnetic currents exist in the interior of the globe."—Ampère.
"The internal heat of our planet is connected with the generation of electro-magnetic currents."—Humboldt.
"A large proportion of winter heat of the poles comes through the equatorial current."—Youmans.
Auroræ.
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 Observatory remarked that the green spectroscopic 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 Wrangel 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."
"These clouds sometimes range themselves even by day in a similar manner to the beams of the aurora and then disturb the course of the magnetic needle in the same manner as the latter. On the morning after every distinct nocturnal aurora the same superimposed strata of clouds have still been observed, that had previously been luminous."
Parry even "saw the great arch of the northern light continue throughout the day."