Disturbance of the Earth’s Magnetism. 149 
in which H’ represented the intensity observed at 10 o’clock, we 
shall have the value of 3 (the dip) corresponding to the latter in- 
tensity. In this way, the change observed in the horizontal intensity 
at the time of the aurora, gives 28’ 48” as the deviation of the 
needle in the plane of the dip. 
The aurora which appeared in connexion with this magnetic dis- 
turbance, was probably one of the most interesting ever observed in 
this country, particularly from the circumstance of the actual forma- 
tion of a corona, which was seen in several parts of this State. My 
friend Prof. Joslin, of Union College, who happened to be in New 
York at the time, has furnished me with the following account : 
“The aurora borealis of 19th April, as it appeared in the city of 
New York at 9 Pp. m., was peculiarly interesting, on account of the 
meeting of the luminous columns in the magnetic meridian, at the 
point in the direction of the dipping needle towards which they usu- 
ally tend. ‘The luminous matter occupied the whole northern half 
of the visible celestial hemisphere, and was very much condensed 
near the point of convergence. Some of the eastern coruscations 
were at times transiently curved, as though their middle parts (as was 
probably the case) were driven eastward by the impulse of the west- 
erly breeze which was blowing at the time. A luminous band was 
at one time extended across the heavens, at right angles to the me- 
ridian, and 30° south of the zenith. This had attimes an oscillatory 
motion ina north and south direction. It passed near the moon, 
around which was one of the large halos. ‘The sky had been previ- 
ously clear. The converging rays appeared to meet at. the star 6 
Leonis.” 
By computing the position of 6 Leonis for 9 o’clock on the eve- 
ning of the 19th, its altitude was found to be 70° 25’, and it azimuth 
11° 27 east. A small error in time, however, would make a great 
difference in the azimuth. ‘The dip of the needle at New York is 
73°, and the variation probably between 4° and 5°, as it is 62° at 
Albany. a 
The aurora was also seen by Dr. William Campbell, at Cherry 
Valley. He describes it as very brilliant, and assuming a variety of 
forms ; at one time appearing as a stupendous arch, crossing the 
heavens from east to west; at another, radiating from a point south 
of the zenith. The Rev. Mr. Thummel, of the Hartwick Seminary, 
at his residence in Otsego county, likewise observed the same aurora. 
He describes it as radiating in every direction from a nucleus near 
