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writings of Tromholt, the author proceeded to discuss the 
following problems connected with it : —Firstly, the geographical 
distribution ; secondly, its height above the earth; thirdly, the 
meaning of the regular formations observed in the phenomena it 
displays ; and, fourthly, as to the cause of the colour and the 
variations of it which give it such beauty. 
1. As to the geographical distribution. It is well-known 
that the Aurora increases in frequency and intensity as we 
leave the equator and approach the poles. But in the Northern 
Hemisphere, Professor Fritz, of Zurich, has shown that there 
is'a maximum zone. This runs from Point Barrow over Great 
Bear Lake to Hudson’s Bay, over Main on the coast of 
Labrador, south of Coast Farewell in Greenland, between 
Iceland and the Faroe Islands, across the Lofaden Islands, 
the North Cape, north point of Nova Zembla, and south of 
Wrangel-land. During the dark season in this zone the Aurora is 
a phenomenon of almost daily occurrence. A line drawn from 
point to point as indicated above coincides almost exactly with 
the northern limit of trees. Extended observation has shown 
that the brilliancy and frequency of the Aurora in North latitudes 
generally varies roughly with the number and size of the spots on 
the sun, or the intensity of its facule. That is to say, that its 
period of greatest brilliancy conicides with the maximum sun-spot 
period and comes about every eleven -years. The Aurore of 1859 
and 1871 and 1872 were very remarkable. At the same time the 
electrical disturbances in the telegraph cables were very extra- 
ordinary. 
2. What is the height of the Aurora above the Earth? The 
evidence here is most conflicting and varies between six miles 
(Franklin), and an extreme limit of 1,006 miles (Tompson), 
Probably the majority of Auroral displays take place at about 70 
or 100 miles. 
3. As to the regularity observed in its forms. The arc is the 
more constant of these. Asa rule the higher the arc the wider 
apart are its extremities, the narrower it is, the more intense the 
light. Next are the Auroral bands. These are generally nearer 
the zenith than the arc, and consist of streamers of luminous 
matter, or of clouds with a peculiar phosphorescent glow, and 
often showing all the colours of the rainbow. Then we have 
streamers or bands of light darting vertically upwards, and then 
many parallel to the horizon. But the grandest phase of the 
Aurora is when the streamers play from all parts of the heavens 
oa? the magnetic zenith, forming a huge dome or cupola of 
ame. 
Lastly, as to the cause of the glow of the Aurora and of its 
magnificent colouring, white, green, orange, and red. Of these 
