424 Mr. Dal ton on the Height of the Aurora 



the angle was found to be 61°. I then fixed the axis at 70°; 

 this he was almost certain was too high. When it was fixed 

 at 50°, he was still more certain it was too low. 



The aurora was seen at Manchester, as has been stated ; 

 but it does not appear to have attracted much attention at this 

 place. I have not been able to trace any account of the phe- 

 nomena having been seen further south. 



These are all the material observations I have collected; 

 from which it must appear that the descriptions every where 

 given evidently apply to the same luminous arch. In proceed- 

 ing from north to south we find the arch gradually advancing 

 in altitude, always crossing the meridian to the south of the 

 zenith, till we arrive about Kendal, at which place it crossed 

 nearly in the zenith, and when at Warrington its culminating 

 was to the north of the zenith. It is further remarkable, that in 

 all the places the arch seemed to terminate nearly in the mag- 

 netic east and west, or at two opposite points of the horizon ; 

 these facts indicated the great height and extension of the 

 arch. 



In order to apply the data to calculate the height of the 

 arch, it is evident that observations at the extremities of the 

 magnetic meridians are to be preferred, and those on or near 

 the same meridian, all other circumstances being the same. 

 Unfortunately, the Edinburgh and Hawick observations do 

 not harmonize together : however, those at Jedburgh, a place 

 nearly of the same latitude as Hawick, seem to show that both 

 the others are wrong, or rather perhaps, that they had not 

 been cotemporary with each other and the rest of the obser- 

 vations. The Hawick altitude is probably too low, and that 

 at Edinburgh considerably too high. 



In this uncertainty we may be allowed to take the observa- 

 tions at Whitehaven and Warrington as guides. Those places 

 are very nearly on the same magnetic meridian ; they are di- 

 stant eighty-three miles, giving an extensive base : the obser- 

 vations were nearly cotemporary, and made on the same part 

 of the arch, the altitude at Whitehaven being 75° from the 

 south, and that at Warrington 61° from the north. From 

 these data, I find the height of the arch very nearly one hun- 

 dred miles above the earth's surface, and its position vertical 

 about Kendal and Kirkby-Stephen, which accords well with 

 the observations at those places. This conclusion is corro- 

 borated by the observations at Jedburgh and Warrington, 

 where, if we take the angles of elevation at 60° and 61° re- 

 spectively, and the distance on the magnetic meridian 120 

 miles, the height will be found between 100 and 110 miles. 

 But, lastly, if we assume the angle at Edinburgh to be correct 



at 



