248 abstracts: geology 



serves to cany any difference which there may be in the secondary 

 currents. 



The detector should be sensitive to 0.00005 ampere. The moving 

 coil of a commercial wattmeter, the current coil of which is separately 

 excited, is suitable for this purpose. 



Two modifications of the general method are described in detail in 

 the paper. F. B. S. 



« 



PHYSICAL CHEMISTRY.— (7as interferometer calibration. J. D. 

 Edwards. Bureau of Standards Scientific Paper No. 316. 1917. 

 The Rayleigh-Zeiss gas interferometer which finds numerous appli- 

 cations' in precision and technical gas analysis is usually calibrated by 

 means of gas mixtures analyzed by chemical methods. The new 

 method here proposed requires only the use of a pressure gage and a 

 knowledge of the refractive indices of the gases for which the calibra- 

 tion is desired. It is based upon the relation between the density and 

 the refractivity of a gas and the relation between the composition and 

 refractivity of gas mixtures. J. D. E. 



GEOLOGY. — Phosphatic oil shales near Dell and Dillon, Beaverhead 



County, Montana. C. F. Bowen. U. S. Geological Survey 



Bulletin 661-1. Pp. 6. 1918. 



The oil shale that promises to be valuable occurs south of Dillon, 



Montana, at about the same horizon as the phosphate deposits of 



Montana, Idaho, and Wyoming and, in addition to the oil it yields, 



contains considerable phosphate. Laboratory tests have shown that 



the phosphate is not driven off by distillation, and the fact that the 



shale yields oil on distillation and yet retains a notable quantity of 



phosphate in the ash presents to the technologist a problem whose 



solution may be of economic value. R. W. Stone. 



GEOLOGY. — Gold placers of the Anvik-Andreafski regioyi, Alaska. 



George L. Harrington. U. S. Geological Survey Bulletin 



662-F. Pp. 17, with geologic sketch map. 1917. 



Paying placers have been found on both sides of a greenstone ridge 



intruded by granitic rocks. Quartz veins related in origin to the 



intrusives are the source of the gold. Other mineral resources are 



coal and mineral springs. G. L. H. 



