1630 Fig-are of the Sun. 



1640 Figure of the Planets (separately for each Planet). 



1660 Figure of Satellites, inch RingSj'stem of Saturn. 



1680 Fig-Lire of Comets and Meteoric Streams. 



1700 Perturbed Rotation ; Reaction on other Bodies. 



1710 Precession and Nutation of the Earth. {See also 



0260, 3320). 

 1720 Movement of the Poles on the Surface of the 



Earth. 

 1730 Libration of the Moon. (See also 4830). 



1740 Libration of Planets and Satellites. 



1750 Theory of Tides. (.S'ee a/so J 41, 95). 



1770 Constitution of the Solar System. 



1780 General Laws of Distribution of Planets and 



Comets. 

 1790 Origin, Stability, Development of the System. 



Stellar Universe. 



1800 Greneral. 



1810 Structure of the Universe ; Stellar Systems. 



1820 Theory of Double Stars ; Calculation ^of Orbits. 



1830 Resisting Medium , Ether,Temperature of the Universe. 



1840 Motion of Solar System in Space. 



PRACTICAL ASTRONOMY. 

 Observatories, Instruments and Methods of Observation. 



2000 Observatories (General). 



2010 History, Situation, Description, Reports, Per- 



sonnel, etc. 

 2020 Observator}^ Buildings. 



Domes, Piers, Rising- Floors and Observing- 

 Chairs, Portable Huts, etc. 

 2030 Instruments (Genei'al). 



Old Instruments, Astrolabes, etc. 

 2040 Objectives : Glass and Manufacture of Glass, Com- 



parison of Reflectors and Refractors. (See also 

 C 3000-3100). 



Optical Matters, Images, Diaphragms, Screens. 

 Visual Refractoi-s. 

 Photographic Refi-actors. 

 Photographic Doublets. 

 Mirrors. 

 2050 Equatorial Mountings (Description etc.) and Driving 



Clocks. 



Visual Refractors, Photographic Refractors. 



Photographic Doublets (Portrait Lenses). 



Mirrors. 



Heliometer. 



Heliostats, Coelostats. 



Driving Clocks, Control Pendulums, etc. 



