Disturbance of the Earth’s Magnetism. 151 
form continued streaks of light in every part of the visible heavens. 
The corona, according to this hypothesis, is the perspective projec- 
tion on the sky, of the beams which are shooting up at the same in- 
stant on all sides of the observer, and which, being all parallel to the 
dipping needle, appear to converge as it were to a vanishing point, 
situated, in the State of New York, about 15° south of the zenith. 
If this hypothesis be correct, and it seems a strict geometrical deduc- 
tion from actual appearances, it would follow, that on the evening of 
the 19th of April, beams of auroral matter, were shooting up from 
every part of the surface of the State of New York. 
But the most interesting circumstance in reference to this aurora, 
is that which I have learned from the December number of the Jour- 
nal of the Royal Institution of Great Britain, viz. the fact of a dis- 
turbance of terrestrial magnetism being observed by Mr. Christie in 
England, on the same evening, and at nearly the same time the dis- 
turbance was witnessed in Albany, and that too in connection with 
the appearance of an aurora. 
Mr. Christie had adjusted a magnetic needle for the express pur- 
pose of observing the effect when an aurora should appear, but was 
not so fortunate as to be able to make any observations with it until 
the evening of the 19th of April. His apparatus consisted of a light 
needle six inches long, suspended within a compass box by a fine 
brass wire ;1, of an inch in diameter, and twenty three inches long. 
The needle was deflected from the magnetic meridian by the repul- 
sive action of two bar magnets placed on opposite sides of it; so that, 
instead of pointing to the magnetic north, it settled in the direction of 
N. 37° W. As the needle assumed this position in consequence of 
the attractive force of the earth, and the repulsive force of the mag- 
nets, a deviation from the north towards the west would indicate a 
diminution of the terrestrial horizontal intensity, and a deviation 
towards the north an increase in that intensity, the intensity of the 
magnets remaining the same. At 10 o’clock p. m. on the evening 
ef the 19th, during the appearance of the aurora, Mr. Christie found 
the needle vibrating between N. 43° 40’ W. and N. 42° 40’ W. 
At 10h. 15m. its direction was N. 34° W. It continued to approach 
the north until 10h. 37m. when it pointed N. 33° 30’ W. It again 
receded from the pole, and at 10h. 40m. vibrated between N. 37° 
W. and N. 36° W. The next morning at 7h. 20m. the needle 
pointed N. 40° W. From this brief abstract of Mr. Christie’s ob- 
servations, it will be seen that the horizontal intensity was less than 
