186 PROCEEDINGS OF THE AMERICAN ACADEMY 



although no auroral light was seen ; and by the kindness of Mr. Cleve- 

 land Abbe, of the Signal Corps, I learn that no aurora was reported 

 for that night. 



It is not a new thing to see vibrations and pulsations running along 

 the tails of comets. Many observers have seen this phenomenon ; 

 among others, Longomontanus, Vandelin, Snellius, and Father Cysat, 

 who are reported to have seen undulations taking place in the border 

 of the comet of 1618, as if it was agitated by the wind. Hevelius 

 observed analogous motions in the comets of 1652 and 1661. Pingre 

 asserted that he distinctly saw, in the long tail of the comet of 1769, 

 *' des ondulations semblables a celles que les aurores boreales present- 

 ent." * According to Winnecke, from the 5th to the 12th of October, 

 1858, the rays forming the superior part of Donati's comet spread and 

 contracted suddenly, like the rays of the aurora. 



Cambridge, Jan. 5, 1877. 



» Arago, Astro. Popu., vol. ii. p. 439, Paris, 1855. 



