IV. An Account of feveral extraordinary Meteors or Lights in the 
Sky. By Dr. Edmund Halley, Savilian Profeffor of G conic* 
try at Oxon, and Secretary to the Royal-Society. 
T H E Theory of the Air feemeth, at prefent, to be perfed- 
ly well underftood, and the differing Denfities there- * 
of at all Altitudes, both by Reafon and Experiment are fuffi- 
ciently defined ; for fuppofing the fame Air to occupy Spaces 
reciprocally proportional to the Quantity of the fuperior or 
incumbent Air, I have elle where proved that at 40 Miles high 
the Air is rarer than at the Surface of the Earth about 3000 
times; and that the utmoll Height of the Atmofphere, which 
refleds Light in the Crepufculum, is not fully 45 Miles Noc- 
withftanding which, ’tis ftill manifeft that fome fort of Va- 
pours, and thofe in no fmall Quantity, arife nearly to that 
Height. An Inftance of this may be given in the great Light: 
the Society had an account of (vid.Tranfatf.Se pt. 1676) from 
Dr. Wallis , which was feen in very diftant Counties almoft 
over all the South Part of England '• Of which though the 
Dodor could not get fo particular a Relation, as was requifite 
to determine the Height thereof, yet from the diftant Places 
it was feen in, it could not but be very many Miles high. 
So likewifethat Meteor which was feen in 1708. on the 31 ft 
of July, between Nine and Ten a Clock at Night, was evi- 
dently between 40 and yo Miles perpendicularly high, and as 
near as I can gather, over Sherenejs and the Buoy on the More . 
For it was feen at London moving horizontally from E. by M. 
to E. by S. at Jeaft 50 Degrees high, and at Redgrave in 
Suffolk, on th eParmouth Road, about 10 Mi'es from the Eaft 
Coaft of England, and at leaft 40 Miles to the Eaftward 
of London , it appeared a little to the Weftwards of the 
South, fuppofe S. by W. and was feen about 30 Degrees high, 
Hiding obliquely downwards. I was fhown in both Places 
the Situation thereof, which was as deferibed, bi^t could 
wifn fome Perfon skill’d in Aftronomical Matters had feen it, 
Cc z that 
