Mijcettanea Curio fa ^ 27 



Ingrefs, and the other at the Egrefs) but fell 

 (and that alfo parallel) on the Eye. That the 

 Rays were tingd with Colours by thofe Re- 

 fractions, after the fame manner as we fee they 

 are by a Glafs Prifme. That the Secondary Iris 

 is produced, after the fame manner, by the 

 Rays that fall more obliquely, only here are 

 Two Reflexions, before the Sun's Rays (which 

 when refracted a Second time proceed parallel 

 to the Eye) emerge out of the Drops of Wa- 

 ter. Further, that the Magnitude of each Iris 

 depends upon the Degrees of the Refradion, 

 which is different according to the Nature of 

 each tranfparent Solid or Liquid. 



And fuppofing the Proportion of the Sines 

 of the Angles of Incidence to the Sines of the 

 refraded Angles, to be in Water, as 250, to 

 187, he determined the Semi-Diameter of each 

 Iris, agreeably to Obfervations, viz.. that of 

 the Primary Iris, 41 °. 30'. and that of the 

 Secundary, 51 0 . 54'. By which he did not fo 

 much confirm the Theory it felf, which was 

 demonftrated from other Principles, as the 

 Truth of the fore -mentioned affnmed Proportion, 

 (viz? that of the Refradion.) But for thefe 

 Things, the Reader may confult the 8th Chap- 

 ter of Cartes'* Meteors, whither I refer him. 



But now Cartes (who ufed an indired and 

 tentative Method in determining thefe Angles) 

 did not feem clearly to apprehend the Ealinefs 

 of the Problem he had propofed to himfelf. 

 And becaufe none (that I know ofj fince him, 

 has handled the fame Argument more fully ; 

 and alfo fince fome have mifunderftood what 

 Cartes did, committing very great Paralogifms, 

 in fome Books (fince his time) whkh particu- 

 larly 



