[ 8i8 ] 
planum squatoris, in vim DR perpendicularem ad 
planum orbits fatellitis, et in vim SR jacentem in 
eodem piano. Producatur SR donee occurrat CK 
in K, eritque SK normalis ad CK, et planum SDK 
normale ad planum orbis fatellitis ; ac propterea ob 
fimilia triangula SDK, SRD, fi m denotet finum ad 
radium i et n cofinum anguli SKD, inclination^ 
fcilicet orbits fatellitis ad squatorem planets, erit 
DR = SD x n = et SR = SD x m = 
exiftente i gravitate tota fatellitis in primarium fuum. 
Jam quoniam vis SR jacet in piano- orbits fatellitis, 
hujus plani fitum non mutat ; accclerat quidem vel 
retardat motum fatellitis revolventis, fed hsc accele- 
ratio vel retardatio ob brevitatem temporis ad quan- 
titatem fenfibilem non exurgit : vis DR eidem piano 
perpendiculars continue mutat ejus fitum, et motum 
nodi generat, quern fequenti propofitione definiemus. 
PROPOSITIO II. 
Proelema. 
Invenire motum nodi ex preediffd caufd criundum . 
Per motum nodi in hac propofitione intelligo mo- 
tum interfedtionis plan or um squatoris planets et or- 
bits fatellitis; orbitam autem fatellitis quamproxime 
circularem fuppono. Edo S locus latellitis in orbe 
fuo SN cujus centrum C, (Fig. 4.) SF arcus centro 
C deferiptus perpendicularis in circuluin squatoris 
planets FN ; SB arcus eodem centro deferiptus per- 
pendicularis ad orbem SN, atque in SB fumatur 
lineola Sr squalis duplo fpatio, quod fatelles per- 
currere poffet impellente vi DR in Coroll, prsccd. 
7 deter- * 
