CONTENTS. 



CHAP. VII. page 24.1. 

 Of Vifion. 



:e deferred as an optical InJ}rument.Drftti of the Eye. Short 

 and weak Sight. The former remedied by double csnca-ve, and the 

 latter by double con-vex, Glares. How the Faculty of feeing correct- 

 ly is acquired. Apparent Magnitude depends en the Dijlance of Ob 

 jiJ.'s. Vifual Angle. Phenomena of Fijion. I'/hy the dijlant 

 Parts of an horizontal Plain, and of the Sea, appear elevated. 

 Why a long Wall appears curved. Why a high Tower appear $ 

 falling to an Eye beneath. Belt of Saturn, Phenomena of Fijian at 

 tonne fled with Motion. Why the Moon cppears to move injlead of 

 the Clouds which pafs over its Face. Why a Circle viewed ob- 

 lia^uely appears oval. How Glajfes ajjlji the Sight. 



CHAP. VIII. page 250. 

 Of Telefcopes and other Optical Inilruments. 



Principles on which thefe Injiruments are conJtru8ed t Defec~ls.Tele- 

 fcope of Galileo. Micrbfcope.Refcfllng Telefcope. Camera Qb- 

 J'cura. Magic Lanthorn. 



CHAP. IX. page 260. 

 Of the different Refrangibility of the Rays of Light, and of 



Colours. 



Errors ad Inconveniencies in optical Injiruments from the Refrafliott 

 of Light. Neivton, while attempting 'to remedy thefe, difcovers a 

 ne~w Property in Light. Phenomena and Caufe of Colours.' Achro- 

 matic TelcJ'cope. The Eye an achromatic optical Inftrument. Ex- 

 periments en Colours. Cauft of the permanent Colour of opakt 

 Bodies. 



CHAP. X. page 276. 



Of the Rainbow, and other remarkable Phenomena of Light. 

 Of the primary and feccndan Rainbow. Why the Phenomenon affitmit. 

 the Fcrm of an Arch. At what Angles the different Colours are 

 apparent. Lunar Rainbow. Marine Bow. Coloured Bowsfeen 

 on the Ground. Halo or Corcna. Curious Phenomena Jeen on the 

 yfy of the Cordtleras. Similar Appearance in Scotland. Parhelia, 

 or Mock Suns. Singular Lunar Phenomenon. Blue Colour of the 

 Atmcj'phere. Red Colour of the Morning and Evening Clouds. 

 Colour of tht Sea. 



CHAP. XI. page 293. 

 Of the Infleftion of Light. 



Retrofpecl of the Dotfrine of Rejleclion. Nature of Inflexion. New- 

 ton's Experiments. Analogy between this Property and Refraflion. 

 Curious Ef efts from this Property. 



BOK 



