200 COSMOS. 



that has become difficult to answer, since impHcit confidenco 

 is no longer yielded to the relations of Greenland whale-fish- 

 ers and Siberian fox-hunters. Northern lights appear to have 

 become less noisy since their occurrences have been more ac- 

 curately recorded. Parry, Franklin, and Richardson, near 

 the north polo ; Thienemann in Iceland ; Gieseke in Green- 

 land ; Lottn. and Bravais, near the North Cape ; Wrangel 

 and Anjou, on the coast of the Polar Sea, have together seen 

 the Aurora thousands of times, but never heard any sound 

 attending the phenomenon. If this negative testimony should 

 not be deemed equivalent to the positive counter-evidence of 

 Hearne on the mouth of the Copper River and of Henderson 

 in Iceland, it must be remembered that, although Hood heard 

 a noise as of quickly-moved musket-balls and a slight crack- 

 ing sound during an Aurora, he also noticed the same noise 

 on the following day, when there was no northern light to be 

 seen ; and it must not be forgotten that Wrangel and Gieseke 

 were fully convinced that the sound they had heard was to 

 be ascribed to the contraction of the ice and the crust of the 

 snow on the sudden cooling of the atmosphere. The belief 

 in a crackling sound has arisen, not among the people gener- 

 ally, but rather among learned travelers, because in earlier 

 times the northern light was declared to be an efiect of atmos- 

 pheric electricity, on account of the luminous manifestation 

 of the electricity in rarefied space, and the observers found it 

 easy to hear what they wished to hear. Recent experiments 

 with very sensitive electrometers have hitherto, contrary to 

 the expectation generally entertained, yielded only negative 

 results. The condition of the electricity in the atmosphere.* 



* [Mr. James Glaisher, of tlie Royal Observatory, Greenwich, iii his 

 interesting Remarks on the Weather d7iring the Quarter ending' Decem- 

 ber 31st, 1847, says, " It is a fact well worthy of notice, that from the 

 beginning of this quarter till the 20th of December, the electricity of 

 the atmosphere was almost always iu a neutral state, so that no signs of 

 electi'icity were shown for several days together by any of the electric- 

 al instruments." During this period there were eight exhibitions of 

 the Aurora Borealis, of which one was the peculiarly bright display of 

 the meteor on the 24th of October. These frequent exhibitions of brill- 

 iant Aurone seem to depend upon many remarkable meteorological re- 

 lations, for we find, according to Mr. Glaisher's statement in the paper 

 to which we have already alluded, that the previous fifty years afFoi'd 

 nc parallel season to the closing one of 1847. The mean temperature 

 of evaporation and of the dew point, the mean elastic force of vapor, 

 the mean reading of the barometer, and the mean daily range of the 

 readings of the thermometers iu air, were all greater at Greenwich 

 during that season of 1847 than the average range of many pi'ececliiig 

 years.] — Tr. 



