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PHYSICAL GEOGRAPHY. 



Aurora Borealis. 



Bay, speaks of its forming in the zenith, in a shape resembling that of an umbrella, 

 pouring down streams of light from all parts of its periphery, which fell vertically over 

 the hemisphere in every direction. As we retire from the Pole, the phenomenon becomes 

 a rarer occurrence, and is less perfectly and distinctly developed. In September 1828, it 

 was observed in England as a vast arch of silvery light, extending over nearly the whole 

 of the heavens, transient gleams of light separating from the main body of the luminosity ; 

 but in September 1827 its hues were red and brilliant. Dr. Dalton has furnished the 

 following account of an aurora, as observed by him on the 15th of October, 1792: 

 " Attention," he remarks, " was first excited by a remarkably red appearance of the 

 clouds to the south, which afforded sufficient light to read by at 8 o'clock in the evening, 

 though there was no moon nor light in the north. From half-past nine to ten there was 

 a large, luminous, horizontal arch to the southward, and several faint concentric arches 

 northward. It was particularly noticed that all the arches seemed exactly bisected by the 

 plain of the magnetic meridian. At half-past ten o'clock streamers appeared, very low in 

 the south-east, running to and fro from west to east. They increased in number, and 

 began to approach the zenith apparently with an accelerated velocity, when all on a sudden 

 the whole hemisphere was covered with them, and exhibited such an appearance as 

 surpasses all description. The intensity of the light, the prodigious number and volatility 

 of the beams, the grand intermixture of all the prismatic colours in their utmost splendour, 

 variegating the glowing canopy with the most luxuriant and enchanting scenery, afforded 

 an awful, but at the same time the most pleasing and sublime spectacle in nature. -Every 

 one gazed with astonishment, but the uncommon grandeur of the scene only lasted one 

 minute. The variety of colours disappeared, and the beams lost their lateral motion, and 

 were converted into the flashing radiations. The aurora continued for several hours." 

 A copious deposition of dew hard gales in the English Channel and a sudden thaw 

 after great cold in northern regions, are circumstances which have been frequently noticed 

 in connection with auroral displays. 



The sky of the southern hemisphere occasionally exhibits this strange and mysterious 

 light, contrary to an old opinion upon the subject; and here it must be called Aurora 



