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XXX. The Absorption-spectrum, Luminous and Ultra-violet, 

 of large masses of Oxygen. By Professors Liveing and 

 DeWAR*. 



IN the course of experiments on the spectra of gases at high 

 pressures, we have made observations on the absorption- 

 spectrum of oxygen which confirm and extend the observations 

 of Egoroff and Jansen. The interest of this spectrum is so 

 great, on account of the important part which oxygen plays 

 in our world, and its free condition in our atmosphere, and, as 

 we therefore conclude, in the interplanetary space, that it 

 deserves a separate notice. 



In order to include the ultra-violet rays in our observations 

 we have had to contrive windows of quartz to the apparatus 

 containing the gases. A strong steel tube, 165 centim. long 



Section through one end of the tube. 



and 5 centim. wide, was fitted with gun-metal ends, bearing 

 by curved surfaces upon the conical openings of the tube, and 

 forced home by powerful screw-caps. Each gun-metal end 

 was pierced centrally by a conical opening fitted with a quartz 

 stopper, 2'1 centim. thick and of the same diameter, with plane 

 polished ends. A small amount of wax was interposed be- 

 tween the stopper and the gun-metal for the purpose of 

 ensuring a uniform bearing for the quartz, which is very 

 brittle. Trial proved that the tube thus fitted would sustain, 

 without leakage, a pressure of upwards of 260 atmospheres. 

 The tube had, besides, near each end a screw-plug valve for 

 admitting the gases. About the centre of the tube was placed 

 a quartz lens, rather less in diameter than the tube, held in 

 place by three springs which pressed against the walls of the 

 tube. This lens had a focal length of about 46 centim. ; so 

 that when a source of light was placed about 10 centim. from 

 one end of the tube, an image of it was formed on the slit of 

 the spectroscope at about the same distance from the other end 



* Communicated by the Authors. 



