[ l°I J 
X. On the Height of the luminous Arch which was feen on Feb. 
23, 1784. By Henry Cavendifh, Efq. F. R . S. and A.S . 
Read February 25, 1790. 
T HIS arch was obferved, at the fame time, at Cambridge 
by Mr. Wollaston ; at Kimbolton in Huntingdon- 
{hire, by the Rev. Mr. Hutchinson ; and at Blockley near 
Campden in Gloucefterfhire, by Mr. Franklin ; and is de- 
ferred in letters from thofe gentlemen read to the Royal 
Society in December 1786 *. 
It has been remarked, that as the arches of the kind de- 
feribed in thefe Papers have ufually but a very (low motion, 
their height above the furface of the earth may readily be 
determined, provided they are obfervecl about the fame time, 
at places fufficiently diftant ; and they feem to be the only 
meteors of the aurora kind whofe height we have any means 
of afeertaining. 
The three places at which this phenomenon was feen are 
not fo well fuited for this purpofe as might at firft be expe&ed 
from their diftance, becaufe they lie too much in the direction 
of the arch ; they however feem fufficient to determine its 
height within certain limits, and perhaps are as well adapted 
for it as any obfervations we are likely to have of fuch phe- 
nomena. * 
The latitude of Cambridge is 52 0 i 2 / 36" : that of Kim- 
bolton is faid by Mr. Hutchinson to be 52 0 20', and, 
* See p. A',— >4.6. of this Volume. 
2 according; 
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