si ponatur d < r, tum ipfius f expreffio erlt vel pofi- 
t'lva vel negativa vel infinita, prout quanticas 2 d quantitare 
r vel major eft vel minor, vel ci equalis. # 
Si 2 d > r, hoc eft, fi d > tum punftum radians 
& focus ad eafdem partes (peculi jacent. 
^ !Si 2 d <r, vel d < i, tum Imago, in axe ultra (pecu- 
' ■ li verticem produfto, (itaeft. 
' \ $i 1 d = r, vel d= Im-ago infinite diftat, five radium 
reflexus, axi parallelus evadit. 
CmllAM. Calculi hujus ope expedite determinari poteft, - 
quomodo objedli radiantis ( fpcculi refpecflu ) raotui, ipfius 
imagiiiis motus refpondct. Sit (ut antea) Imagints afpecu- 
lo diftantia = quandp objedi diftantia eft d. Mutetur 
jam utcunque objcdi diftantia, & ex d, fiit n d, quantitate 
n Numerum vel integrum velfraftum defignante : & fic loco 
prioris Equationis, f — tj—j babebimus.prp Novo Foco ali- 
am Equationem, F = 7^^. Et quidem fi n Numerum in- 
tegrum exprimere fupponatur, fccunda hxc objedi didantia 
pr im4 major erit, fi vero fit fratftus, tum minor ent prima* 
Hifpe pofitis, fi. d > r, & n fit, integer, eric F <5 f, id eft^ 
crit r~- < TJ^, fiv^e a nddr — ndrr < anddr — 
ana,— r ad — 
df quod manifi^ftum eft. Hoc eft, fi in fpeculo concavo 
objeilli diftantia major fit (emidiametro, tum recedentc objedto 
afpecuio, Imago verfijsfpeculum accedet, R^irfias, dtfignet 
n Numerum fradum, &tuhc reperictur ^nddr-T^ n dr r 
> 2 nddr ~4r!r^ fiy^ F > f. Hqc eft, acced^f^p^Qfta 
ad fpeculum rq^i^^ in}^gp, i hr^m rifl r 
Supponaturjam, d <; ^& alia quaecuaque 61, 0^^(^1 
diftantia nd ^^tel^i^afurea ^etnper niinor cffe quam Tuni 
crunt X n d dr — d r r, & z n d d r — d r r, quantijates ne- 
gative; five ndrr znddr, & drir ~ 2 nddxquajilr, 
titatcs pofitiv2e. Et quidem fi n nuoierq int^gro ^equetur^ 
erit n d r r % o d d r > d r r — 2 n d d r, five F > f 5 fi 
veron fraftiofit, tum erit ndr r — xnddr < drr — 
2 q«dd r, five F < f. Hoc eft, fi in Ipeeulo concaJ^o objecli 
diftantia mioQi^t fpecuU Oiamietfiqu^ turn r^ce-^ 
dente 
