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THE ROYAL SOCIETY OF CANADA 



ends of these tubes plane-parallel and gas-tight up to a pressure of 

 about 120 atmospheres but success was reached at last. By filling 

 both tubes with high-pressure gas and letting the gas out alternately 

 from the two sides the optical compensation will be made quite easy. 



II. Absorption of Light by Oxygen. 



The absorption spectrum of oxygen at high pressures has been 

 studied by Liveing and Dewar\ Olszewski- and others, who found 

 that with a pressure of 85 atmospheres, there was a number of bands 

 in the visible region and a complete absorption in the ultraviolet, 

 beginning about the wave-length X = 2664 Â.U. When the pressure 

 was increased to 140 atmospheres, the bands in the visible were 

 intensified: an additional faint band was brought out in the indigo, 

 and complete ultra-violet absorption now began at the wave-length 

 X = 2704 Â.U. In Liveing and Dewar's experiment, the absorption 

 chamber consisted of a strong steel tube, 65 cm. in length with quartz 

 ends so that the ultra-violet rays were included in their observations. 

 The source of light was placed about the middle of the tube and 

 held in place by means of three springs. This lens was of the required 

 focal length to focus the image of the source on the slit of the spectro- 

 scope. The spectrum so obtained was then photographed. Later 

 they worked with a tube of oxygen 18 metres in length. With this 

 they were able to observe the absorption bands at much lower pres- 

 sures. The quantity of oxygen in the tube at the highest pressure 

 used was about equal to that traversed by the sun's rays in passing 

 through the atmosphere when the sun is vertical. 



This work was repeated with slightly different arrangement of 

 apparatus by Mr. W. W. Shaver^ of the University of Toronto under 



/"/(?. J. 



iLiveing and Dewar, Phil. Mag. 26, p. 387, 1888; Phil. Mag. (5) 34, p. 205, 1892. 



201szewski, Wied. Ann., 42, p. 663, 1891. 



3W. W. Shaver, Trans. Roy. Soc. of Canada, Vol. XV., Third Series, 1921. 



