2070 Meridian Instruments (Mounting- and Description). 



Tran-;it Circle, Visual and Photograpbic. 

 Zenith Telescope, Visual and Photogi-aphic. 

 2080 Extra-Meridian Instruments for Absolute Position, 



Altazimuth. 

 Vertical Ch-cle. 

 Almucantar. 

 Various. 

 2100 Auxiliary Instruments 



Clocks, Chronometers, Watches, Chronographs. 



{See also B 0150). 

 Levels. 

 2120 Eyepieces and Accessories. 



Eyepieces, Illumination, Screens, Solar Eye- 

 pieces, etc. 

 Enlarging Lenses, Correcting- Lenses, etc. 

 Photographic Plate Holders, Exposing Shutters, 

 etc. 

 2140 Micrometers. 



For Visual Telescopes. 



For Measuring Photographs, Solar and Stellar. 

 2200 Spectroscopic Apparatus. 



2210 Objective Pri^m. 



Objective Grating. 

 2220 Solar Spectroscopes and Spectrographs with Slits. 



Eclipse Spectroscoj.^es and Spectrographs. 

 Stellar Spectroscopes and Spectrographs. 

 Spectroscopes and Spectrographs for Study of 



Nebulae. 

 Ocular Spectroscopes. 

 2240 Prism Combinations with Deviation. 



Prism Combinations with Direct Vision. 

 Slit. 

 2250 Auxiliary Apparatus. 



Production of Comparison Spectra. 

 Correcting Lens for Spectroscopic Obser- 

 vations. 

 2260 Micrometer for Visual Observations. 



Micrometer for Measuring Photographic 



Spectra. 

 Miscellaneous. 

 2270 Spectroheliograph and Apparatus for Mono- 



chromatic Images. 

 2280 Theory, Adjustment. 



Comparison of Efficiency of Instruments. 

 2300 Polarization Apparatus. 



2400 Photometry, General. 



Visual. 



Pliot.ogra[ihic. 

 Spectropliol omel ry. 

 2500 Radiometrv (Bolometrv) 



2600 Miscellaneous. 



