( * 5 ° ) 
rejects them as infufficient for that Purpofe ; the Af- 
mofphere being much higher than what has been 
ever found by, them, and confiding of a Fluid much 
finer than the grofs or common Air, the Height of 
which laft only is meafurable by thefeways. 
Mr. Makati therefore goes on to fettle the Alti- 
tude of the Northern Lights , after another manner, 
founded upon feveral Obfervations made at very diftant 
Places at the fame time, and fixes fome Aurora Bo- 
reales to be but one hundred Leagues, though others 
are no lefs than three hundred, and the far greater 
Number of them about two hundred Leagues above 
the Surface of the Earth. 
Mr. Cramer , Profeflbr of the Mathematicks at 
Geneva , computes the Height of the Aurora Bo - 
realis t feen at the fame time at Geneva and Mont - 
pettier ) Feb. iyth, J 1730, to be r££o of a Semidia- 
meter of the Earth, i. e. about 160 Leagues. 
Mr. Meyer has propofed in the Memoires of the 
Academy of Petershurgh, a very ingenious Method 
of finding the Height and Diftance of a Boreal Arc , 
from any Obferver, by a fingle Obfervation. Mr. 
Matron applies this Method to fuch Aurora Boreales 
as were capable of it, and finds that the Boreal Arcs 
of feveral were no lefs than an hundred Leagues 
high. 
It is on this account that in the next Chapter our 
Author confiders fome Solutions that have been offer- 
ed to folve thefe Appearances of the Northern Lights, 
and fets them afide as infufficient, becaufe they fup-, 
pofe Caufes which have no Exiftence, or at leaf! no 
Efficacy at fo great a Height in the Atmofphere. 
The 
