268 HERSCHEL. 



1798. Phil. Trans., vol. Ixxxviii. On the Discovery of Four addi 

 tional Satellites of the Georginm Sidus. The retrograde Motion of its 

 old Satellites announced ; and the Cause of their Disappearance at 

 certain Distances from the Planet explained. 



1799. Phil. Trans., vol. Ixxxix. A Fourth Catalogue of the com 

 parative Brightness of the Stars. 



1800. Phil. Trans, vol. xc. On the Power of penetrating into Space 

 by Telescopes, with a comparative Determination of the Extent of 

 that Power in Natural Vision, and in Telescopes of various Sizes and 

 Constructions; illustrated by select Observations,. Investigation of 

 the Powers of the Prismatic Colours to heat and illuminate Objects; 

 with Remarks that prove the different Refrangibility of radiant Heat; 

 to which is added an Inquiry into the Method of viewing the Sun ad- 

 vantageoiisly with Telescopes of lai ge Apertures and high magnifying 

 Powers. Experiments on the Eefrangibility of the Invisible Rays of 

 the Sun. Experiments on the Solar and on the Terrestrial Rays that 

 occasion Heat; with a comparative View of the Laws to which Light 

 and Heat, or rather the Rays which occasion them, are subject, in 

 order to determine whether they are the same or different. 



1801. Phil. Trans., vol. xci. Observations tending to investigate the 

 Nature of the Sun, in order to find the Causes or Symptoms of its vari 

 able Emission of Light and Heat; with Remarks on the Use that may 

 possibly be drawn from Solar Observations. Additional Observations 

 tending to investigate the S3^mptoms of the variable Emission of the 

 Light and Heat of the Sun; with Trials to set aside darkening Glasses, 

 by transmitting the Solar Rays through Liquids, and a few Remarks 

 to remove Objections that might be made against some of the Argu 

 ments contained in the former paper. 



1802. Phil. Trans., vol. xcii. Observations on the two lately dis 

 covered celestial Bodies (Ceres and Pallas). Catalogue of 500 new 

 Nebulas and Clusters of Stars, with Remarks on the Construction of 

 the Heavens. 



1803. Phil. Trans., vol. xciii. Observations of the Transit of Mer 

 cury over the Disk of the Sun; to which is added an Investigation 

 of the Causes which often prevent the proper Action of Mirrors. 

 Account of the Changes that have happened during the last Twenty- 

 five Years in the relative Situation of Double Stars; with an Investi 

 gation of the Cause to which they are owing. 



1804. Phil. Trans., vol. xciv. Continuation of an Account of the 

 Changes that have happened in the relative Situation of Double 

 Stars. 



1805. Phil. Trans., vol. xcv. Experiments for ascertaining how far 

 Telescopes will enable us to determine very small Angles, and to dis- 



