PROCEEDINGS 



OF THE 



Camktirge ^Ijtbsopljrcal Sfltktg, 



Monday, 27 April, 1896. 



Professor J. J. Thomson, President, in the Chair. 



At a meeting held in the University Chemical Laboratory, the 

 following were elected Fellows of the Society: 



Professor J. B. Bradbury, M.D., Downing College. 

 A. J. Wallis, M.A., Corpus Christi College. 

 C. T. R Wilson, M.A., Sidney Sussex College. 



The following Communications were made: 



(1) On photographing the whole length of a Spectrum at once. 

 By Prof. Liveing. 



Professor Liveing exhibited photographs of a variety of spectra 

 in which the whole length of the spectrum between the wave- 

 lengths 550 and 214 was depicted on a celluloid film at one 

 operation. A concave grating of 10^ feet radius was used, with 

 the slit in the centre of curvature, and the slide which held the 

 sensitive film formed part of a cylinder with a radius of &\ feet, 

 so that, when the axis of this cylinder was midway between the 

 slit and grating, every part of the spectrum was perfectly focussed 

 on the film. The length of the photograph between the limits of 

 wave-length above-mentioned was 65 centimeters. To obviate 

 the confusion caused by the overlapping of the spectra of different 

 orders, he projected on to the slit the image of the source of light 

 by means of a combination of two quartz lenses with a quartz 

 prism of 30° between them. The slit being vertical the edge of 

 the prism was made horizontal, with the result that the more 

 VOL. IX. PT. III. 11 



