RECENT ADVANCES IN SCIENCE 555 



that occur beneath the coastal plain of Louisiana and Texas. 

 He shows that they are arranged along lines related to the 

 main structural features of the region, and that they are 

 accompanied by very sharp and local upthrust and doming 

 of the normally flat-lying sediments. The salt deposits them- 

 selves show intricate folds resembling the flow structures of 

 ancient rocks. Rogers believes that the plugs are offshoots 

 of deeply-buried stratified deposits which have been subjected 

 to great pressure or thrust, and have been squeezed upwards 

 along lines of weakness in a semi-plastic condition. The 

 evidence for their tectonic origin is at least as strong as that 

 for the European salt stocks (Econ. Geol. 191 8, 13, 447-85). 



O. P. Jenkins discusses the origin of two small lakes of 

 epsomite in Washington and British Columbia which present 

 a peculiar spotted appearance owing to numerous shallow 

 pools of brine upon the white epsomite. The origin of the 

 mineral is ascribed to the action oi sulphuric acid, derived from 

 the weathering of pyritic and pyrrhotitic ore deposits, upon 

 the magnesian igneous rocks of the locality (Amer. Jonrn. Set. 



1918, 46, 638-44). 



Whitaker, W., and Thresh, J. C, The Water Supply 

 of Essex from Underground Sources, Mem. Geol. Surv. 191 6, 

 pp. 510. 



Hall, A. L., On the Mode of Occurrence and Distribu- 

 tion of Asbestos in the Transvaal, Trans. Geol. Soc. South 



Africa, 191 8, 21, 1-36. 



Wagner, P. A., Reports on Certain Minerals used in the 

 Arts and Industries. I. — Asbestos, South African Journal 

 of Industries, Industrial Bull. Ser. No. 6, Nov. 191 7 (191 8), 

 pp. 22. II.— Magnesite, ibid., Bull. No. 12, March 191 8, pp. 11. 



Stratigraphical and Regional Geology.— A stratigraphical 

 point of some importance is discussed by Prof. E. C. Case in 

 a paper on Permo-Carboniferous Conditions versus Permo- 

 Carboniferous Time (Journ. Geol. 191 8, 26, S°°-6). It was 

 prompted by the observation that " Permo-Carboniferous Con- 

 ditions " (red beds with reptilian and amphibian fauna) 

 appeared much lower in the stratigraphic sequence in the 

 east of the United States than in the west. This is explained 

 as due to the fact that an environment favourable to the 

 development of a certain fauna begins in a limited area and 

 spreads slowly, thereby involving different levels of one or 



