_Light is not reflected by impinging against the solid parts of bodies_ p. 339 _The particles which compose bodies are transparent_ p. 341 _Cause of opacity_ p. 342 _Why bodies in the open day-light have different colours_ p. 344 _The great porosity of bodies considered_ p. 355 ~CHAP. 3.~ _Of the refraction, reflection, and inflection of light._ _Rays of different colours are differently refracted_ p. 357 _The sine of the angle of incidence in each kind of rays bears a given proportion to the sine of refraction_ p. 361 _The proportion between the refractive powers in different bodies_ p. 366 _Unctuous bodies refract most in proportion to their density_ p. 368 _The action between light and bodies is mutual_ p. 369 _Light has alternate fits of easy transmission and reflection_ p. 371 _The fits found to return alternately many thousand times_ p. 375 _Why bodies reflect part of the light incident upon them and transmit another part_ ibid. _Sir_ ~ISAAC NEWTON~_’s conjecture concerning the cause of this alternate reflection and transmission of light_ p. 376 _The inflection of light_ p. 377 ~CHAP. 4.~ _Of optic glasses._ _How the rays of light are refracted by a spherical surface of glass_ p. 378 _How they are refracted by two such surfaces_ p. 380 _How the image of objects is formed by a convex glass_ p. 381 _Why convex glasses help the sight in old age, and concave glasses assist short-sighted people_ p. 383 _The manner in which vision is performed by the eye_ p. 385 _Of telescopes with two convex glasses_ p. 386 _Of telescopes with four convex glasses_ p. 388 _Of telescopes with one convex and one concave glass_ ibid. _Of microscopes_ p. 389 _Of the imperfection of telescopes arising from the different refrangibility of the light_ p. 390 _Of the reflecting telescope_ p. 393 ~CHAP. 5.~ _Of the rainbow_ _Of the inner rainbow_ p. 394 395 398 399 _Of the outter bow_ p. 396 397 400 _Of a particular appearance in the inner rainbow_ p. 401 _Conclusion_ p. 405 ~ERRATA.~