BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 617 



Subject-Index. Piulosopiucal Transactions. Tear. Page. 



Nebulous stars : jqqo .-aq 



• 1814 255 



Nebulous strata : their origin I735 254 



Newton: "'."/.'^./.'"'.^^^ 1795 46 



Newton's riugs : iu general 1307 180 



'■ 1809 259 



= 1810 149 



Nucleus of a Comet : definition Ig03 146 



Oberon : discovered Jan. 11, 1787 (period 13^ days) 1787 126 



: its elements 1 730 S ■^^^ 



I 377 



: is brighter than Titania 1788 376 



: is variable in brightness 1815 355 



: revolves in 13*1 111^ 8™ 59' I815 350' 



Obser\^atiou^ : are made to philosophize upon, and to communicate 1784 438 



: 1785 213 



: practical hints for observing. See Methods of observing. 



Olbers: 1807 260 



Optical illusion in viewing the moon 1795 53 



Orion : the trapezium is not connected with the nebula 1791 77 



Pallas : observations 1802 213 



:' its diameter is 147 miles. 



Parallactic motions : of stars iu general .". 1805 233 



Parallax of the Sun, Stars, etc. : see Sun, Stars, etc. 



Perihelion passage of a Comet : its eflfect 1812 140 



: - 1812 235 



Periodicity of Solar Spots : is connected with the price of wheat 1801 310 



Phases of Comet 1807, I 1808 156 



Photometry: Table of the transmission of terrestrial scattered light 



through various substances, etc 1800 528 



: 1300 533 



: 1800 534 



Photometry of Stars : methods 1806 208 



: See Catalogues of the Comparative Brightness, etc, 



PiGOTT: 1796 177 



Planetary Nebula} 1802 501 



Planets : all are probably self-luminous to some degree 1795 50 



: defined 1802 224 



: their evolution 1812 143 



Pores: iu the Sun 1801 292 



Price of wheat : its connection with Sun spots 1801 310 



Probable errors : see Errors. 



Proper motions: of nebulte 1814 249 



Proper motion : of the sun, star.s, etc. See Sun, Stars, etc. 



Proper motions of Stars : theii- cause 1606 225 



Radiant Heat : see Heat. 



Red Stars : see Stars. 



Reflecting telescopes : see Telescopes. 



Refrangibility of heat, etc. : see Heat. 



Resisting medium l''^! 117 



: may stop some light 1~82 104 



Resolution of the milky way, etc. : see Milky Way. 



