GEOPHYSICAL LABORATORY. 173 



recognized, the first as a constant establishing a datum level for the refrin- 

 gence and the second as a function of one or more terms expressing the course of 

 dispersion throughout the visible spectrum. These conclusions follow directly 

 from the analysis of the hnear relations which have been shown to exist be- 

 tween the partial dispersions of a series of optical glasses. They prove that a 

 rise in the partial dispersion at any part of the spectrum is accompanied by 

 a corresponding rise in partial dispersion over the entire visible spectrum. 



(423) The wave-lensths of X-rays. Ralph W. G. Wyckoff. J. Wash. Acad. Sci., 11, 



366-373 (1921). 



It is shown in this paper that, taking the case of sodium chloride as typical, 

 there are other structures beside the commonly accepted "sodium-chloride 

 arrangement" which are in agreement with the present experimental data. 

 As a result of this lack of definiteness, it is more logical to consider the value 

 of the wave-lengths of X-rays as based upon the quantum hypothesis. 



(424) Silica-glass prism for refractometry of liquids at elevated temperatures. F. R. 



V. Bichowsky and H. E. Merwin. J. Opt. Soc. Amer., 5, 441-443 (1921). 



Optically prepared plates of silica-glass were beveled together to form a 

 prism having angles of 45°, 60°, and 75°. The plates were held together in a 

 graphite holder and united by fusing the edges in an oxj^-gas flame. The 

 prism was used in an electrically heated goniometer furnace, and the dis- 

 persions of sulphuric acid, acetic acid, chloronaphthalene, and sulphur deter- 

 mined at suitable temperatures between 25° and 350°. 



(425) Kilauea gases, 1919. E. S. Shepherd. Bull. Hawaiian Volcano Observatory, 9, 



83-88 (1921). 



Twenty-five samples of gas collected at Kilauea between 1912 and 1919 have 

 been analj'zed. The results to date permit the following generaUzations : 



The major emanation from this volcano is water (H2O), the average of water 

 in all analyses being about 70 per cent of the total gas evolved. Second in 

 order of magnitude comes carbon dioxide (CO2), with sulphur dioxide (SO2) 

 following in third place. Sulphur trioxide (SO3) occurs in variable amounts, 

 in one instance rising to 5 per cent, whereas in the two samples from Mauna 

 Loa it reached the high value of 8 per cent. Sulphur, while usually small in 

 quantity, sometimes rises as high as 8 per cent. 



In general, the 1917 collection, obtained by Shepherd from floating crusts 

 at the lake edge, contains higher amounts of hydrogen (H2) and carbon mon- 

 oxide (CO) than the gases of 1918-19 obtained from a variety of sources by 

 Dr. Jaggar. The general inference is, however, that quite regardless of the 

 source from which the gas is obtained, it reaches the surface almost completely 

 burned, or else is actively burning in the surface layer of the lake. Probably 

 both mechanisms obtain. 



The ratio of argon to nitrogen is about three times as great as in atmospheric 

 nitrogen. Helium and neon have been positively identified, though the 

 amounts were not notablj' larger than in residues from air. Chlorine occurs, 

 but in relatively small amount. Whether fluorine is present could not be 

 satisfactorily tested in such volumes of gas as we here dealt with, but there 

 was evidence in the 1912 collection that it w^as present in about twice the 

 amount of chlorine. Hydrocarbons are apparently absent, or else present in 

 inappreciable quantity. 



The water present may well be partly due to oxidation of evolved hydrogen, 

 but such oxidation must occur in the body of the lava lake, presumably near 

 the surface. It does not seem probable that this combination could occur at 

 the actual surface, since any such quantities of hydrogen as would be implied 



