1 185 ] 
XXV. A Letter to the Rev. Nevil Mafke- 
lyne, F. R. S. AJlronomer Royal , from 
Mr. Bailly, of the Royal Academy of 
Sciences at Paris : Containing a Propofal 
of fane new Methods of improving the 
Theory of Jupiter’s Satellites . Tranfated 
from the French, with the Original un- 
derneath. 
S I R, 
Read Feb. 18 and JT 
2 S » *775* 
"'HOUGH I have not the ho- 
nour of being per fon ally known 
to you, I hatter mylelf, you will excufe the liberty I 
have taken, of communicating to you two methods, 
of my invention, for perfecting the theory of the 
fatellites of Jupiter. The former of thefe methods 
ferves to meafure their diameters, and the latter is 
Intended to make the obfervations comparable with 
each other,, though made in different places, and 
with different inftruments. As my intention has 
been 
Mon fie ur, 
Quoique je n r aye pas l’honneur d’etre connu de vows, je penfe,, 
que vous ne trouverez pas mauvais, que je prenne la fiberte de vous 
communiquer deux irethodes, quej’ai imaginees, pour perfect. ■»* 
cnner la theorie des f'atellites de Jupiter.. La premiere de ces 
n ethodes fen a. mefurer leur diametre, et la feeonde a pour ob- 
jet de rendre les obfervations comparables, foit quelles aient: 
Lifts. en diSerens lieux. et avec differens inifoumentn. 
MoiU 
