252 JOURNEY TO THE SHORES 



The aurora appeared with more or less 

 brilliancy on twenty eight nights in this 



parent altitude 2° 35' 20", the mean refraction is 

 16' 5" (Maekay's Tables), and the true, found as de- 

 tailed above, is 20' 8" : which increasing in the same 

 ratio as that of the atmosphere, at a mean state of 

 temperature, is 41' 19" at the horizon. But the dif- 

 ference of refraction at the upper and lower limbs, 

 increasing also in that ratio, gives 55' 16" for the 

 horizontal refraction. Temperature of the air —41°, 

 Wind north, a light breeze, a large halo visible about 

 the sun. January 15th, 1821. — Observed an appa- 

 rent meridian altitude 0 lower limb 4° 24' 57"* Q 

 apparent diameter 31' 5". For apparent altitude 

 4° 24' 57", the mean refraction is 10' 58" (Maekay's 

 Tables), and the true, found as detailed above, is 

 14' 39", which, increasing in the same ratio as that of 

 the atmosphere at a mean state of temperature, is 

 43' 57" at the horizon. But the difference of refrac- 

 tion between the upper and lower limbs, increasing 

 also in that ratio, gives 48' 30" for the horizontal re- 

 fraction. 



" Temperature of the air— 35°, a light air from the 

 westward, very clear. 



" The extreme coldness of the weather rendered 

 these operations difficult and dangerous ; yet I think 

 the observations may be depended upon within 30", as 

 will appear by their approximate results in calculating 



