ON THE AURORA BOREALIS 



AT FORT ENTERPRISE, 

 EXTRACTED FROM THE JOURNAL OF LIEUTENANT ROBERT HOOD, R. N. 



During the summer of 1820, the Aurora was only once visible before the 

 month of August, when the nightly temperature of the air was generally below 

 50°. The late continuance of day-light, and the few opportunities which we 

 had of making observations at the most favourable hours, render it possible 

 that the Aurora may have sometimes appeared, in this long interval, without 

 our knowledge. But those opportunities were sufficiently numerous to con- 

 vince me, that it is actually very seldom present in these regions during the 

 summer. 



The number of Aurora visible in August 1820, was ten ; in September six ; 

 in October seven ; in November eight ; in December twenty ; in January 

 1821, seventeen; in February twenty -two ; in March twenty-five; in April 

 eighteen ; and in May, the brightness of twilight prevented us from seeing 

 more than nine. The whole amount is more than double the number of our 

 observations at Cumberland-House. It is worthy of remark, that the number 

 of Aurora in each month of both the winters, bears some proportion to the 

 thermometrical range. The shapes of the Aurora at its entry into the horizon, 

 and progress through the sky, may be reduced under two general descriptions. 

 In the first, I shall class those which are formed like rainbows or arches, in the 

 earliest stage of their appearance. They rise with their centres, sometimes 

 in the magnetic meridian, and sometimes several degrees to the eastward or 

 westward of it. The number, visible at the same time, seldom exceeds five, 

 and is seldom limited to one. The altitude of the lowest, when first seen, is 

 never less than 4°. As they advance towards the zenith, their centres (or the 

 parts most elevated,) preserve a course nearly in the magnetic meridian, or 

 parallel to it. But the eastern and western extremities vary their respective 

 distances, and the arches become irregularly broad streams in the zenith, each 

 dividing the sky into two unequal parts, but never crossing one another till 



