No. III.] 



Dr. RICHARDSON ON THE AURORA. 



605 



arch to its former dimensions was equally gradual with its dilatation. The arch 

 was occasionally divided into five parallel beams, which, having a direction 

 nearly from north to south, traversed it obliquely. These beams had a quick 

 lateral motion, and were sometimes gathered into masses that receded so far 

 from each other, as to break the arch into several portions, which had pointed 

 extremities arising from the obliquity of the beams which composed them. 

 The length of the beams was sometimes considerably increased by their 

 northern extremities shooting up, whilst their lower ends remained stationary. 

 These appearances were but of momentary duration, the beams rapidly 

 re-uniting to form a homogeneous arch. 



After the Aurora had continued for about half an hour to display a succes- 

 sion of the above forms, the arch totally disappeared, and a horizontal mass 

 of light was observed in the southern quarter of the sky, having its face 

 longitudinally barred by several thin strata of clouds. 



At 10jh., there were various irregular masses of light scattered over the sky, 

 but most luminous in the north. The Aurora had appeared early in the night 

 hv the west, afterwards its most luminous parts were collected in the south, 

 about nine, it shone most brightly in the eastern quarter of the sky, and now, 

 as we have just mentioned, its principal seat was in the north. 



December Uth, 1820. 



Hour. Temp. Wind. 



A.M. 9-33 N.E. Fresh, hazy, small snow. 



Noon -25 do. do. do. do. Very little mist at the rapid. 



P.M. 9-31 N.N.E. Moderate. clear. Bright moonlight. 

 Midnt. -31 do. do. do. Rapid very loud. 



At 5h. p. m., several broad arches of rare light appeared, extending from 

 N.W. to S.E. At six, they disappeared, no change of the weather having 

 occurred in the interim, the sky remaining clear, with a bright moon. At nine, 

 an arch was formed in the east, broad, irregular, and rather faint. Its 

 extremities bore north and S.E., and were spirally twisted near the horizon. 



At 10jh., there was an arch in the southern quarter of the sky, 40° high. 

 Its extremities had an equal breadth with its centre, and bore N.W. and S.E. 

 respectively. Wind a little more northerly— sky clear. 



At Uh., two bright arches passed near the zenith in a direction from N.W. 



