164 



NA TURE 



[June 15, 1893 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, March 9. — "On the Geometrical Con- 

 struction of the Oxygen Absorption Lines Great A, Great B, 

 and o of the Solar S|)ectium." By George Higgs. Communi- 

 caled hy R. T. Glazebrook, F. R.S. 



In the early part of August, 1890, the photo^rjphic work of 



The differences of wave-length between the components ot 

 pairs increase in the same order. 



These and other properties, which will be referred to, are 

 still more obvious in the trains or fiutings, 



Fr.jm ils holding an intermediate rank in each of its distin- 

 guishing characters I was induced to adopt Bas a typical group 

 in a geomelrical representali(?n, and to investigate the subject by 

 means of rectangular co ordinates. 



Fig. I. 



the normal solar spectrum which I had undertaken had been 

 carried as far as great A, or the limit of visibility in the red, 

 and to A 8350, or beyond z, in the invisible region?. 



During the two previous months of continuously dull weather, 

 while classifying and comparing results, I was interested, on 

 making a close examination of the head portion of the A line, 

 to find, the rhythmical yroitpinp, t'le liarnimic order of se- 



Before a complete analysis could be made out, a micrometer 

 had to be completed. This cmsisted of a platform, serving as a 

 plate holder, which was mide to travel on runners between 

 parallel ways by means of a screw of such a pitch as to move the 

 negative from one division of the scale to the next, for one re- 

 voluti in of Ihedivided plate.on the screw head, this la;t;r being 

 divided into 100 parts. 



Fic. 2. 



quence, and other characteristics of the B line repeated here in 

 every detail. 



These two bands, together with alpha, are composed of a 

 number of doublets or pairs, which approach each other on the 

 more refrangible side with uninterrupted regularity, finally cross- 

 ing, and at the limiting edges of all three bands the three last 

 pairs overlap each other. 



NO. 1233, VOL. 48] 



On and over the platform, a microscope is mounted with slide 

 motions at right angles to each other ; an index of glass fibre and 

 rellector complete the apparatus. 



Over icoo measurements of nearly 200 lines have been made, 

 100 of which belong to great A, these together with the com- 

 puted positions are contained in the Proc. Royal Soc. 



In the analysis the axis of x is assumed to occupy a position 



