and the motion of Auroral Beams. 39 



These observations indicate that the minimum deviation of 

 the magnetic needle advances like a wave over the earth's sur- 

 face; and that the direction of its motion is from N. 69° E. to 

 S. 69° W. A comparison of the Cambridge and Toronto ob- 

 servations indicates a velocity of progress amounting to 156 

 miles per minute ; while a comparison of the Philadelphia and 

 Toronto observations indicates a velocity of only 103 miles per 

 minute. 



yie thus see that the average progress of the maxima and 

 minima deviations of the magnetic needle was very nearly in 

 the same direction and with the same velocity. Assuming that 

 the average direction of both classes of waves is the same, we 

 find their progress to be from N. 68° E. to S. 68° W. ; and the 

 velocity of their progress deduced from a comparison of the 

 Cambridge and Toronto observations is 134 miles per minute; 

 while the velocity deduced from a comparison of the Philadel- 

 phia and Toronto observations is 89 miles per minute. 



In my former article, p. 334, I found that in Central Europe, 

 the deflections of the magnetic needle were propagated in a di- 

 rection from N. 28° E. to S. 28° W. Mr. C. V. Walker deter- 

 mined that the direction of this motion in England was from 

 N. 42° E. to S. 42° W. ; and we now find this direction in the 

 neighborhood of New York to be from K 68° E. to S. 68° W. 



At the time of a considerable number of the preceding ob- 

 servations, auroras were recorded at some one of the stations, 

 i-he following are the auroral notices at Toronto, corresponding 

 to some of the preceding dates. The dates are all given in the 



!0f Go 



1840. 



May 



ottingen. 



Auroral observations at Toronto. 

 5^. Faint light in north. 

 I5h 16™, faint streamers shot up from N.E. to altitude 



16b sm, a perfect arch from N.W. to NJ:. Splendid 

 streamers rising from it, and almost a continued 

 gleam of light from the incessant flashes or pulsations. 



UK Streamers disappeared ; faint patches of light and 

 a few pulsations. 



18h. Very faint light arch, dark clouds rising in N. 

 horizon. 



19h. Bright aurora. 



20h. Bright aurora. 

 A'Ug. 28. 14b 30". Splendid aurora. 



15^. Aurora visible at intervals. 



I7h SOni. Aurora very splendid. 



ISii, Auroral light obscured by the clouds, 



19l». Overcast. 



21h. Cleared up; aurora again visible. 



