3*5
His tribus obtufis facierum flexibus extant
Compofiti ; aft omnes alii fex fronte retufi
2015
Sunt tantum cx una , fed frontibus exacuuntur
E geminis : facile in crudas diffinditur idem
Ad quodvis latus haud prona ratione locatas,
Ejus fed lateris diflentas in regionem.
Exfurgens cruftre facies nitida ipfa manebit,
2020
Prorfus ubique tamen non requa, fed afpera paulum .
Prreterea facile eft: etiam interradere mollem ;
Durum opus at faciem prorium eft inferre, politam ,
Mollitiem hanc propter nimiam : vitroque polire
Tentabis lato m e lius , quam forte metallo,
2025
Aut laxo fuper excurrens, poterifquc cavatos
Radendo fulcos implere , & reddere frevem
Poft oleove terens , aut ovi albente liquo re :
His potis eft opibus frons pellucere polita .
Nunc 1age,fac radium in quamcumq. incurrere fronte, 2030
Rcdlumvc, obliquumve velis*, tum protinus ipfo
Ingreflu in geminum difeinditur unus; ut illam
Si trans cryftallum perarata evolvere verba
Incipias, horum geminata elementa tuaris;
A t -
L I B E R N O N U S .
r. A d d u cit ja m
h ic jp fa m p r o
prietatem A n g u la re m e ju s c ry fta l-
li , q u am ib id em N e v v t o n u s fic
p r o p o n it ,, Si h u ju s la p id is c r y -
ffallini fr u flu m lib r o typ is im -
,, prello i m p o n a t u r > J ittc rx fin -
„ g u lx p er c r y fta llu m ifta m in -
,, F p e & x g e m in a q u a d a m re fr a -
j,
ftio n c v id e b u n tu r b i n x
,
et
fi
j, quis lu m in is ra d iu s in q u arn -
„ libet ejus fu p e rfic ic m in c id a t
,, vel ad p e rp e n d ic u lu m , v e l q u o -
„ vis o b liq u o a n g u lo ; d iv id itu r
,, is c o n tin u o g e m in a ifta re fra -
, , ftio n e in d uos radio s , q u o -
,, rum q u id e m r a d io ru m u te r q u e
„ eodem e ft c o l o r e , a c ip.se ra -
,, dius in c id e n s , & in te r fe ct-
,, lam pares ad q u a n tita te m lu -
„ m i n i s , v e l ferin e pares vid e n -
,, t u r . D u a r u m ift a r u m re fra -
,, ftio n u m altera c o m o d o cffici-
t u r , q u o m o d o c x u ficatis opei-
„
cx
le gib u s effici d e b e t , ita
„ n i m i r u m , u t finus in c id e m u s
,, c x aere in
h a n c c r y fta llu m
„ ca m h a b e a t ra tio n e m ad fin u m
„ r e fr a ftio n is , q u a m h a b e n t
**
ad 3.
A lt e r a ,
q u x appellari
„ p o te ft re frad tio in u fitata , effi-
,, cicur se q u e n ti l e g e .
H i c N c v v t o n u s d e te rm in a t o -
p e sch em a tis & d ifta n tia m alte
rius radii a b a l t e r o ,
S c
p la g a m ,
in q u ara t e n d i t . E t q u id e m pla
g a ipsa fin e fc.hem atc e x p rim i n o n
p o te ft , nifi ita o b fc u r c , ut n ih il
lic e a t p e r c ip e r e . Q u a m o b r e m N o
fte r illud ta n t u m m o d o expreffie ,
ra d iu m in u fitata le g e r c t r a f t u m
d irig i in c e r t a m , & c o n ft a n t c m
p la g a m refpedtu radii r e fr a & i le
g e u fitata : q u o d a u t e m p e rtin e t
ad d iftan tiam , d i c i t , c a m in pla
n o o p p o fito effe c ir c it e r p a rte m
o f t a y a m d ift a n t ix p l a n o r u m . E ft
