Opticks 1717 - Up

~xwer tA the Obje 11 the Focus of the
leai? refrangible ones 9 by about the s?f-th part
of the difiarlce between the Obje&-glafs and the
Focus of the mean sefiangiblc ones.
And if Rays of all forts, flowing from ally
one lucid point in the Axis of any umvex Lens,
bc made by the Refra&ion of the kens to tollverge
to points not too reniot~ fro111 the Lens,
the FOCUS of the inoft refrai-rgible Rays ihall be
nearer to the Lens than the FOCUS of the leafi
refrangible ones , by’s dii’cance which is to the
274th part of the difiance of the ~‘QCUS of the
mea11 refrangible Rays from the LcnS as the difhnce
bem7ee11 that Focus and the luc.id oint
from whence the Rays flov7 is to the dii P Aance
between that iucid point and the Lens very’ ‘
amine whether the difference be-’
fra&tions which the moit &km& !
blc and the kafi refrangible &I’ s flow~.~~g~i-om
the fame point fuffeer in the C Y bjecd’c-glalks~ of
Telefcopcs and fuch like GMIks, be .6 great a$’
is here d’efcribcd, E contrived the fol.lowingE&
periment.
Expr. 16 The Lens which X wkd in the fe,
eond and eighth Experiments, being pln~d iix
Feet and an I& diitant from any OlrjcA, c&
&Aed the Species qf that Obje& by the mean
refrangible Rays at the dii?ance of Gx :I/‘Icct aa&
cl1 Inch from the LenB on the otk3 Me. Ancf
therefore by the foregoing Rule it ought to CC&~
le& the Species of that ObjeB by the lc:zit se-f
fialigible Rays ‘at the diftalrce of iix V’cer amt.
3-i- Inches fi:om the Lens, qd by the rnoit I+
fmgi blc