34 8 NINETEENTH CENTURY. PT. in. 



feet in all, and representing photographs of between ten 

 and twenty million of stars. With such a result as this we 

 may well close our short sketch of the work which light 

 has done and is doing for astronomy. They were results 

 little dreamed of when Davy proposed to take sun-pictures, 

 and Fraunhofer measured the dark lines in the spectrum, 

 and they have been obtained step by step through honest 

 patient work both in the improvement of instruments and 

 in daily and hourly accurate observation and experiment 



Chief Works consulted. Roscoe's ' Spectrum Analysis ; ' * Edin- 

 burgh Review,' vol. cxvi. ; 'Philosophical Magazine,' 1860 ; Proctor, 

 ' The Sun ; ' Tyndall's ' Lectures on Light ; ' ' Half-hours with Modern 

 Scientists;' Kirchhoff's 'Researches on the Solar Spectrum,' 1862; 

 'Encyclopaedia Britannica,' art. 'Optics;' Ganot's 'Physics;' Wol- 

 laston, 'On Dispersion ' ' Phil. Trans.' 1 802 ; Lockyer, The Spec- 

 troscope;' Miss Clerke, 'Astronomy of the Nineteenth Century;' 

 Common, ' Astronomical Photography,' Nineteenth Century, Feb. 1887. 



