t^ Anali/aes of Books, [July^ 



Hia^jnotie meridian ; in another, the beam shot up from the mag- 

 netic north to the zenith ; and in both these cases, the need^ 

 moved towards the west." 



" The needle was most disturbed on February 13 [1821], p.m, 

 at a time when the Aurora was distinctly seen passing between 

 a stratum of clouds and the earth, or at least illuminating the 

 face of the clouds, opposed to the observer. This and several 

 other appearances, recorded in the accompanying notes, induced 

 me to infer that the distance of the Aurora from the earth varied 

 on different nights, and produced a proportionate effect on the 

 needle. When the light shone through a dense hazy atmosphere, 

 when there was a halo round the moon, or when a small snow 

 was falling, the disturbance was generally considerable; and on 

 certain hazy cloudy nights, the needle frequently deviated in a 

 considerable degree, although the Aurora was not visible at the 

 time. Our observations do not enable us to decide whether this 

 ought to be attributed to an Aurora concealed by a cloud or 

 haze, or entirely to the state of the atmosphere. Similar devia- 

 tions have been observed in the day-time, both in a clear and 

 cloudy state of the sky, but more n-equently in the latter case. 

 Upon one occasion, the Aurora was seen immediately after sun- 

 set, while bright day-light was remaining." 



" A circumstance to which I attach some importance must not 

 be omitted. Clouds have been sometimes observed during the 

 day to assume the forms of the Aurora, and I am inclined to 

 connect with the appearance of these clouds the deviations of 

 the needle, which ^vas occasionally remarked at such times.'* 



" An Aurora sometimes approached the zenith, without pro^ 

 ducing any change in the position of the needle, as was more 

 p;enerally the case, while at other times a considerable alteration 

 took place, although the beams or arches did not come near the 

 zenith. The Aurora was frequently seen without producing any 

 perceptible effect on the needle. At such times its appearance 

 was that of an arch or an horizontal stream of dense yellowish 

 light, with little or no internal motion.'* 



" The disturbance in the needle was not always proportionate 

 to the agitation of the Aurora, but it was always greater 

 when the quick motion and vivid light were observed to take 

 place in a hazy atmosphere." 



" In a few instances, the motion of the needle was observed 

 to commence at the instant a beam darted upwards from the 

 horizon. And its former position was more quickly or slowly 

 regained according to circumstances. If an arch was formed 

 immediately afterwards, having its extremities placed on op- 

 posite sides of the magnetic north and south to the former one, 

 the return of the needle was more speedy, and it generally went 

 J)eyond the point from whence it first started." 



i* When tne disturbance of the needle was considevable, it 



