5 o 8 Mr. herschel’s Agronomical Obfervations 
fequences, which might not appear at firft ; fuch as the 
great probability, not to fay almoft abfolute certainty, of 
her being inhabited, we fhall foon agree, that thefe 
refearches are far from being trifling. 
My reafon for repeating obfervations that have been 
made by very good aftronomers was not that I doubted 
either their veracity or diligence. The names of Gali- 
leo, hevelius, kircher, and feveral more, will always 
■deferve to be mentioned with particular refpeCt for the 
eminent fervices they have rendered to aftronomy ; but 
as we know that their inftruments were far from being 
arrived to that degree of perfection we have, now ob- 
tained, I thought it by no means improper or ufelefs to 
repeat their obfervations cm the lunar mountains, and to 
extend them to other parts of- the Moon’s vifible hemi- 
. ; - X 
fphere., and thereby to eftablifli this theory on the 
firmed evidence of , a furvey taken by a very excellent 
iaftrument. > 
The method ufed by hevelius and others to find the 
height of a mountain in the Moon is this. Let a ray of 
light slm (fig. i.) proceeding from the Sun, pafs by 
the Moon at l, and touch the top of a mountain at m : then 
the fpace between l and m will appear dark, and the top 
of the mountain will be feen to Hand at feme diftance 
from the illuminated part of the Moon’s difk. With a 
7 good 
