294 



CATALOGUE. PHYSICAL OPTICS. 



Hpmberg on the force of light. A. P. 1708. 



H. 21. 

 Maiian on the velocity of light. A. P. 1738. 



37. H.82. 



Aberration. 



Bradley on a newly discovered motion of the 



stars. Ph. tr. 1728. XXXV. 637. 

 Clairaut on the aberration of the stars, 



planets, and comets. A. P. 1737. 205. H. 



76. 1746. 539. H. 101. 

 Euler on the phenomena aiising from the 



progressive motion of light. C. Petr. XI. 



150. 



Assumes the projectile hypothesis of light for its simpli- 

 city, but observes, that in some cases the phenomena are 

 different on the different suppositions. 



Winthrop and Price on planetary aberra- 

 tion. Ph. tr. 1770. 358, 536. 



Boscovich on the aberration of light. Op. 

 ined. V. 417. 



fjeaurat on the planetary aberration of light. 

 A. P. 1786. 572. 



Robison on the motion of refracting medi- 

 ums. Ed. tr. II. 83. 



Corrects some errors of Boscovich. 



Some mistakes appear to have been made respecting this 

 subject : they may be avoided by attending to one general 

 principle ; that is, when a body moves uniformly forwards, 

 the relative situation of another body, whether quiescent or 

 in motion, appears at all times to be such as it really was at 

 the moment of the emission of the light of the second body: 

 in other words, neglecting the changes in the earth's mo- 

 tion, during the passage of the light, the apparent place 

 of the sun, or of any star or planet, is its true geocentric 

 place for the instant at which the light was emitted by the 

 sun or star, or reflected by the planet. Y. 



Decay of Light. 



Pb.tr. 1794-. 



Light is found to diminish in intensity as the squares of 

 the distances increase, or a little faster. Rumford. 



Interception and partial Reflec- 

 tion of Light. 



See Shadows. 

 Gregory on oblique reflection. Birch. III. 



79. 

 Bouguer Optique. 



The moon reflects about ^ of the light that falls on it, 

 Bouguer found that water reflected J^ of the light falling 

 perpendicularly, quicksilver -!| or .683. At an inclination 

 of 50° quicksilver reflected only 32 timet as much as water. 



Kurdwanowski's problems respecting light. 

 Ace. A. P. 1732. H. 95. 

 On the degree of illumination. 



Krafft on the reflection of light by a trans- 

 parent medium. C. Petr. X. 183. 



fEdwards on reflection. Ph. tr. 1763.229. 



On the reflection of light by transparent 

 mediums. Roz. III. 27. 1 16. 



Dionis du S^jour on the quantity of light 

 falling on the moon in eclipses, and on 

 the faint light of the new moon. A. P. 

 1776. 



The faint light is a minimum at 43° elongation, a maxi- 

 mum at 0° and at 69° : at 90° it is about half the greatest 

 quantity. 



Count Rumford found that a pane of plate glass stopped 

 .1973 parts of the light; another .1869; two together .3184; 

 apiece of thin window glass stopped .1263. In reflection 

 from a glass mirror .35 was lost, .65 being reflected : this 

 is but little less than was reflected in Bougucr's experiment 

 by quicksilver only. 



Refractive Powers. 

 J. A. Porta de refractione. 4. 

 Lahire on the refraction of ice. A. P. IX. 

 328. X. 172. 



Less refractive than water. 



Lahire on the refraction of oil and water. A. 



P. IX. 382. 

 Lowthorp on the refraction of air. Ph. tr. 



1699. XXI. 339. 

 Cassini on the refraction of air. A. P. 1700. 



78. H. 112. 



■ s ;' 



