268 ‘ HERSCHEL. 
1798. Phil. Trans., vol. lxxxviiii—On the Discovery of Four addi- 
tional Satellites of the Georgium 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. lxxxix.—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 ac- 
vantageously with Telescopes of large Apertures and high magnifying 
Powers.—Experiments on the Refrangibility 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 Symptoms 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. xciii—Observations on the two lately dis- 
covered celestial Bodies (Ceres and Pallas).—Catalogue of 500 new 
Nebule and Clusters of Stars, with Remarks on the Construction of 
the Heavens. 
1808. 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. xev.—Experiments for ascertaining how far 
Telescopes will enable us to determine very small Angles, and to dis- 
