576 KEPOBT — 1888. 



SATURDAY, SEPTEMBER 8. 

 The followoDg Papers and Report were read : — 



Department for Light and Electricitt. 



1. bur V application de V analyse spedrale a la mecanique moleculaire et sur 

 les spectres de Voxygene. By Dr. J. Janssen. — See Reports, p. 547. 



2. On the Absorption Spectrum of Oxygen} By Professors Liveing, F.It.S., 



and Dewar, F.B.8. 



The authors describe the ahsorption spectrum given by oxygen at various 

 pressures up to 165 atmospheres in a tube, fitted with quartz ends, 1'6 metre long, 

 and at pressures from one to ninety atmospheres in a tube 18 metres long. They 

 confirm generally the results of EgorofF and Janssen, and add some new facts with 

 regard to the absorptions in the more refrangible part of the spectrum. 



Of all the absorptions Fraunhofer's A required the least amount of oxygen to 

 produce it in sufficient intensity to be seen, and B came next. All the other ab- 

 sorptions in the visible region seem to be represented, but with less intensity, 

 amongst the telluric bands of the solar spectrum. Neither carbonic acid gas nor 

 nitrous oxide gave any visible absorption. A could not be resolved into lines, 

 because the expansion of the lines with increased density of the oxygen obliterated 

 the interspaces. The rapid increase in the strength of the bands with increasing 

 pressure of the gas accords with Janssen's law that the intensity of the unresolv- 

 able absorptions varies as the square of the density of the gas. 



With the shorter tube at high pressures the authors found that the absorption 

 of ultra-violet rays beyond A 2665 was complete, while with the longer column 

 the complete absorption extended much lower, to about X 3360. 



Remarkable efi'ects were observed to arise from variations of density in the gas, 

 the tube becoming quite opaque through internal reflexions when it was heated at 

 one or two points or when gas at high pressure was entering the tube rapidly. 



The Spectra of Meteorites compared ivith the Solar Spectrum. 

 By J. Norman Lockter, F.B.S. 



4. On the Harmonic Series of Lines in the Spectra of the Elements. 

 By Professor Carl Runge. 



Similar to the formula found by Mr. Balmer, of Zurich,^ in 1885 for the wave- 

 len"-ths of thirteen lines of the hydrogen spectrum there exist, as Professor Kayser 

 and I have found, formulas for the groups of lines of other elements, which Pro- 

 fessors Liveing and Dewar have called ' harmonic series of lines,' and which they 

 Lave compared t© the series of overtones emitted by a vibrating elastic body. 



The formulas have the form 



wave-lengtli = — ; ., 



a + bn~^ + en ■* 



or wave-length = = — ^ ,, 



a + on— + en'* 



where a, h, c are constants and n assumes consecutive values of the series of entire 

 numbers. 1 give an example of a series of eight lines in the spectrum of lithium 

 observed by Liveing and Dewar : — 



' For full details see Phil. Mag. Sept. 1888, and Cheni. News, vol. Iviii. p. 163. 

 ' Wiedemann's Annalen, 25, pp. 80-87. 



