360 Prof. J. Dewar. The Specific Volumes of Oxygen 



those of a Cygni was pointed out. Later, Mr. McClean* confirmed 

 this, and further stated that the bright lines of 77 Argus corresponded 

 with the dark lines of the Nova ; while later still, Sir David GiUf has 

 shown the similarity between the spectra of rj Argus and Nova Aurigse. 

 Hence we are led to the conclusion that the temperatures reached in 

 the outbursts of both these Novae were not greatly different from 

 those of the stars named, and that in t\ Argus there are constant con- 

 ditions which are similar to those temporary conditions which produce 

 the appearance of Novas. 



In the table the lines of Nova Persei are compared with those 

 recorded by Campbell J and Vogel in Nova Aurigse. 



The probably corresponding lines of a Cygni, chromospheric lines, 

 and enhanced lines, are also given in separate columns. 



The reduction to wave-lengths and discussion of the lines in relation 

 ito those of other celestial and terrestrial spectra, has been undertaken 

 !by Mr. F. E. Baxandall, to whom my best thanks are due. 



; ' The Specific Volumes of Oxygen and Nitrogen Vapour at 

 the Boiling-point of Oxygen." By JAMES DEWAK, M.A., 

 D.Sc., LL.D., F.K.S. Eeceived January 21, Bead January 

 30, 1902. 



In my paper on " The Boiling-point of Liquid Hydrogen determined 

 by Hydrogen and Helium Gas Thermometers "|| it was pointed out 

 that a constant-volume gas-thermometer filled with oxygen gas, having 

 a pressure at C. of about 800 mm., gave a very accurate value of 

 the boiling-point of liquid oxygen. As it seemed advisable to confirm 

 this result indirectly, an attempt was made to determine the vapour 

 density of oxygen at its boiling-point by direct weighing, the intention 

 being, if the experimental results proved at all encouraging, to repeat 

 the work on a larger scale and with greater precautions. As at present 

 there is no likelihood of my being able to undertake the more accurate 

 determinations, the results of the preliminary enquiry are presented to 

 the Society. They give in any case, with considerable accuracy, the 

 Specific Volumes which have never been directly determined. 



In order to obviate any question of the buoyancy of the air, two 

 flasks A and B of as nearly as possible the same air displacement were 

 counterpoised on an (Ertling balance. The B flask remained per- 



* ' M.N., E.A.S.,' vol. 61, p. 387. 

 f ' Eoy. Soc. Proc.,' vol. 68, p. 457. 

 % ' Ast. and Ast. Phys.,' vol. 11, p. 808. 

 ' Asfc. and Ast. Phys.,' vol. 12, p. 912. 

 || Eoy. Soc. Proc.,' vol. 68, 1901. 



