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liiis folvere, ut major inde fruaus did queat ; inteU' 
hgatur qums radius feu lucidus, feu fonorus N»G. 
in cujufvis nature curvam, continua fui refra£lione 
rautatus : qusntur qua lege variari fupponenda fit 
denfitas, ■ aut rantas medii in ejus diverfis altitudinibus, 
ut ftante refraaioms theoria, qu* finum refraaionis 
Temper laiitati medii refringentis proportionalem fup- 
ponit, radius ille in talis nature curvam obire potue^ 
rit ? Sit axis curv* N « G, quam radius refraaus ef- 
but, leaa C O, in qua fumpto quolibet ‘ pundo C, 
raibo quovis C L defcribatur quadrans circularis LP^, 
^aaque ubihbet refrafti radii tangente N R, ag(- 
tur ex Q radius did^tangenti parallelus, occurrens StT 
cnJo in P, duftaque P F axi parallda occurrat ordinate 
N Q ad axira perpendiculari inpunao. F,} dico indeor- 
? f tam 
