AURORA BOREALIS. 



223 



after miclni;^lit. This is shown in the following table, in which column first 

 t-hows the hour of observation ; column second shows the number of auroras 

 reported by Captain Lefroy for the year.s 1848 and 1849 at Lpndon, King.ston, 

 Montreal. Quebec, and Newfoundland, in latitudes from 43° to 47.^^ *; column 

 third shows the number observed during the winter of 1857-'58 at Carlton Fort, 

 latitude 52° 52', longitude 106° 30' westt; column fourth shows the number 

 observed during the winter of 1843-'44 at Lake Athabasca, latitude 58° 43' 

 north, longitude 143° 49' west|; column fifth shows the number observed 

 during the winter of 1852-'53 at Point Barrow, latitude 71° 21' north, lon- 

 gitude 156° 15' west§; and column sixth shows the sum of the numbers in the 

 four preceding columns. 



Annual periodicity of auroras. — Auroras occur in each month of the year, 

 but not with equal frequency. This period would be more obvious if it were 

 not disguised by the unequal length of the days in the diflerent seasons. Sup- 

 pose the aurora occurred with equal frequency at every hour of the day and night 

 throughout the year, then the number of those that would be seen in winter 

 must be greater than the number seen in summer, because the prolonged dark- 

 ness permits us to see them more frequently. But, on the contrary, we find in 

 the northern part of the United States more auroras recorded in summer than 

 in winter. This is shown in the following table, in which column second shows 

 the number of auroras observed at New Haven and Boston during a period of 

 113 years, from 1742 to 1854, according to tables recently published by the 

 Connecticut Academy of Arts and Sciences ; column third shows the number of 

 auroras observed at the academies of the State of New York in 25 years, from 

 1826 to 1850 ;|| column fourth shows the number reported by Captain Lefroy 

 for the years 1848 and 1849, in Canada and Newfoundland ;|f and column fifth 

 shows the sum of the numbers in the three preceding columns. 



*N. Y. Reg. Reports, 1850, p. 292. 

 tSt. Helena Mag. Obs., v. 2. p. CX 

 X Lake Athabasca Obs., p. 144. 



§Phi]. Trans., 1857, p. 512. 



II Hough's N. Y. Meteorology, p. 472. 



11 N. Y. Regents' Report, 1850, p. 229. 



