I JO abstracts: spectroscopy 



1. It is based upon the specific gravity values of Plato, which are 

 considered the most reliable of any available. 



2. It is based on 20° C, the most convenient and widely accepted 

 temperature for sugar work. 



3. It is based on the modulus 145, which has already been adopted 

 by the Manufacturing Chemists Association of the United vStates, 

 by the Bureau of vStandards, and by all American manufacturers of 

 hydrometers. H. W. B. 



SPECTROvSCOPY. — Measurements of wave-lengths in the spectrum of 

 neon. Keivin Burns, W. F. Meggers, and P. W. Merrtt.i,. 

 Bur. vStands. vSci. Paper No. 329. Pp. 10. 1918. 



The lines in the neon spectrum are very sharp, a quality which 

 recommends this gas as a standard source wherever the lines have 

 sufficient strength. The ultra-violet group between 3,369A and 3,52oA 

 may be used for standards, and there are a few good infra-red lines, 

 but the strength and distribution of the lines in the region 5,852A to 

 7,438A make the neon spectrum particularly useful as a comparison 

 in this region. 



The wave-lengths of fifty-five lines in the neon spectrum have been 

 measured by means of the interferometer. These lines lie in the region 

 3,369A to 8,495A. The strong lines in the visible region of the spec- 

 trum have been observed with great accuracy, the probable error 

 being one part in several millions, or less than one-tenth the width 

 of the line. These strong lines were observed by means of three differ- 

 ent pairs of interferometer plates which were each used on several 

 interferometers. The ultra-violet lines and all the strong lines in the 

 visible were compared directly with the fundamental standard 6,438A. 

 Some of the deep red and infra-red lines were compared with well- 

 determined lines in the visible neon spectrum. 



One hundred and eighty-nine faint lines in the visible and infra- 

 red neon spectrum have been measured by means of a concave grating. 

 The probable error of these grating measurements is one or two hun- 

 dredths angstrom. The region covered by the grating observations 

 extends from 5,343A to 8,783A. 



The constant differences discovered by Watson are found to hold 

 with remarkable exactness in the case of lines which are strong enough 

 to be measured with the highest accuracy. In fact, the differences 

 are exactly constant within the limits set by the accuracy of the wave- 

 lengths. K. B. 



