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XVI. Account of a luminous Appearance in the Heavens . By 
Mr . Tiberius Cavallo, F. R. S. m a Letter to Sir Jofeph 
Banks, Bart , P. R . & 
Read April 5, 1781. 
I TAKE the liberty to fend you an account of a luminous 
appearance obferved laft night in the heavens, which feems 
to be very fmgular in its nature, and quite diftin 61 from the 
aurora borealis . 
At about half an hour paft nine yefterday evening, being the 
27 th of March, a white light began to be feen in the iky, which 
became gradually more and more denfe till ten o’clock, at which 
time it formed a compleat luminous arch from eaft to weft. 
Of this I have been informed by others ; but at a quarter paft 
ten I went out of the houfe and obferved it myfelf. At that 
time it appeared to be an arch of about feven or eight degrees in 
breadth extended from eaft to weft, or, as fome of my friends 
imagined, in the direction of eaft by north to weft by fouth. 
Itsweftern part quite reached the horizon; but the eaftern part 
of the arch feemed to begin at about 50° or 6o° above the hori- 
zon. It did not pafs through the zenith but at about 8° or io° 
fouthward of it, audit was nearly perpendicular to the horizon. 
The whitenefs of this arch was much denfer than that 
any aurora borealis I ever obferved, though • it did not eaft fo 
much light upon the terreftrial objects. Towards the middle 
it was fo denfe, that the ftars over which it pafled were 
eclipfed ; 
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