4 LANKSHEAR, Quantitative Absorption Spectra. 



glass of known extinction. This is somewhat tedious 

 and does not quite do away with the possibility of error. 

 The central sector acts by cutting down the beam, which 

 nevertheless falls continuously on to the photographic 

 plate. Further, in the Hilger instrument, the greatest 

 length of liquid which can be used is 5 cms. With the 

 new apparatus a Baly tube can be used, and with one 

 solution the extinction coefficient over a wide range of 

 the spectrum can be determined. Finally, because the 

 image is focussed on the slit instead of on the object 

 glass an increased amount of light is obtained in the 

 spectrograph. 



