(■M* > 
The Lumen Boreale ordinarily appears in the Nor* 
them Parts of the Heavens, becaufe tho* the whole 
Atmofphere of the Earth be involved in the Zodia- 
cal Matter (or Solar Atmofphere) yet 'tis thrown 
off both ways, from the Equatorial towards the Polar 
Regions. 
This is owing to a double Caufe, the firft is the 
centrifugal Force, arifing from the diurnal Motion of 
the Earth, which being greateft at the Equator (and 
gradually leffening as you approach the Poles, where it 
vanilhes) makes greateft Oppofition there, and not 
only hinders the Entrance of the Zodiacal Matter 
into the Earth’s Atmofphere, near the Equatorial Regi. 
on, but turns it afide into a Courfe towards each Pole ; 
and the Author does not queftion but an Aurora An- 
Jlralis might be feen at proper times in the Southern 
Temperate Zone, juft as an Aurora Borealis is in 
ours, which is Northern, attended with fimilar Phe- 
nomena, were there but attentive Obfervers. 
The fecond Caufe is the progreffive Motion of the 
Earth in its annual Orbit near one half of the Year 
with the North Pole foremoft, and in the other half 
with the South Pole , moving thro’ the Zodiacal 
Matter. 
The natural Confequence of which will be a heap, 
ing up of Matter, more on the Polar Regions than 
the Equatorial or Temperate, and this accounts in 
part for the Declination of the Centre of the luminous 
Arcs, fometimes near ten Degrees from the Pole j 
the Direftion of this Motion of the Earth not coinci. 
ding with the Direction of the Axis of the Earth, 
at thofe times. 
The 
