83 On the Height of the Aurora Borealis. 



situated only five or even ten miles above the earth's surface, 

 appeared as far to the south of the zenith as at Edinburgh, or 

 rather further." — " Unfortunately the Edinburgh and Hawick 

 observations do not hai'monize together ; however, those at 

 Jedburgh, a place of nearly the same latitude as Hawick, seem 

 to shew that both the others are wrong, or rather, perhaps, 

 that they had not been contemporary with each other and 

 the rest of the observations. The Hawick altitude is probably 

 too low, and that at Edinburgh considerably too high.'' 



From the seeming impossibility of arriving at any conclu- 

 sions from accounts with such discrepancies, the Doctor re- 

 jects these observations altogether, although, apparently, 

 they were otherwise entitled to full credit, as the situation of 

 the arch is pointed out in reference to certain stars, <tc. ; and 

 he adopts the observations at Whitehaven and Warrington as 

 the basis of his calculation. 



At Whitehaven the altitude seems to have been taken with 

 no more care than at the former places, as it is said that at 

 8^ 45>" the arch was about 15' south of the zenith. « At 9'' 8'" 

 the arch moved southward." 



At Warrington, the method of taking the altitude is very 

 unsatisfactory. Dr Dalton says, his friend, Mr Crossfield, in- 

 formed him that " he saw the arch about nine o'clock, or be- 

 tween that and ten. At the first glance he took it for the 

 milky way, but soon discovered his mistake. The direction 

 of the arch was from WSW. to ENE., passing to the north 

 of the zenith. The western branch Avas longer and more bril- 

 liant. He saw no northern lights at the time, neither did he 

 apprehend the phenomenon was connected with them. On 

 elevating the pole of a celestial globe till the axis passed 

 through a series of angles with the horizon, I desired him to 

 fix upon an elevation which he judged most nearly to coincide 

 with the elevation of the centre of the luminous arch. On 

 examination, the angle was found to be Gl°. I fixed the 

 angle at 70° ; this he was almost certain was too high. When 

 it was fixed at 50°, he was still more certain that it was too 

 low.'' 



From these observations, Dr Dalton calculated the arch 

 was 100 miles high, or S or 9 miles in width. 



