0. C. Lester — Oxygen Absorption Bands. 147 



Art. XX. — On the Oxygen Absorption Bands of the Solar 

 Spectrum; by O. C. Lester.* ("With Plates II, III 

 and IY.) 



The present research was undertaken with the object of 

 investigating as fully as possible the structure and extent of 

 the oxygen absorption spectrum. This includes a study of 

 the relations existing between the lines of a band and also 

 between the several bands, taking into account those groups 

 above a which do not seem to have been considered before. In 

 order to do this satisfactorily it was necessary to have very 

 accurate measurements of the wave lengths. The best deter- 

 minations previously made are those of Rowland and Higgs, 

 but neither gives all the lines even of the groups A, B, and a. 

 Rowland's measurements are nearly complete for B, but he 

 gives only a few for the other two groups. Higgs gives A 

 and B and up to the ninth pair of a, and although he and 

 Rowland agree remarkably well in general upon B, judging 

 from the few lines in A which both have measured the agree- 

 ment is not so good, there being much greater discrepancies 

 than one would expect from the accuracy claimed for their 

 measurements. Hence it seemed worth while to make new 

 determinations of all, or nearly all, the lines previously meas- 

 ured, and in addition many new lines are given. It is hoped, 

 therefore, that the present determination of the wave lengths, 

 taking into account the best previous results, have both 

 extended and unified the measurements on these bands and 

 rendered them, on the whole, more accurate ; thus doing for 

 the absorption spectrum of oxygen what a similar work of 

 M. Eisigf has done for the line spectrum. 



Because of the precision which it is possible to attain in the 

 measurement of this spectrum, a careful study of the relations 

 subsisting between the lines and bands furnishes an excellent 

 test of the so-called laws of Deslandres for band spectra. They 

 are briefly as follows : 



1. In a given band the intervals from one line to the follow- 

 ing in any series, calculated in vibration numbers, are in arith- 

 metical progression, i. e., the lines are connected by a relation 

 of the form 



-1 = N =■«+&*" 



A 



* Abstract of a thesis presented to the Philosophical Faculty of Yale 

 University, June, 1904, for the degree of Doctor of Philosophy. The paper 

 will appear in extenso in the September number of the Astrophysical 

 Journal. 



|M. Eisig : Das Linienspektrum des Sauerstoffs, Wied. Ann., li, 1894. 



