384 SCIENCE PROGRESS 



industrial uses for which refractory sands are required will 

 also be much appreciated by geologists. 



Under an unpromising title, L. Reinecke (Non-bituminous 

 Road Materials, Econ. GeoL, 191 8, 13, 5 57— 97) presents the 

 best modern study of road metals, including the methods of 

 investigation, and geological considerations in highway con- 

 struction. 



In a study of the barite deposits of Missouri, W. A. Tarr 

 (Econ. GeoL, 191 9, 14, 46-67) describes the mineral as occur- 

 ring in veins, disseminated deposits, sink-hole or cave deposits, 

 and residual deposits, of which the last-named are the most 

 productive. The deposition of barite by circulating ground 

 waters is considered improbable ; and the view that ascending 

 thermal solutions deriving their barium from deep-seated 

 igneous rocks are responsible for the primary deposits of the 

 mineral is favoured. 



In an investigation of the potash salts of the Punjab Salt 

 Range and of Kohat, Stuart (Records, GeoL Sitrv., India, 1919, 

 50, pt. 1, 28-56) arrives at the conclusions that no continuous 

 bed of potash is to be found in these localities. The rock-salt 

 is foliated, and the contained potash occurs in discontinuous 

 lenticles and irregular folia. 



This work led to a new hypothesis as to the origin and 

 history of the rock salt and gypsum of the same regions (ibid. 

 PP- 57 _ S9)- While the salt was originally sedimentary, the 

 nature of the banding, the frequent lenticular 'arrangement, 

 the striking flow structure, and the nature of the associated 

 salt marl beds show that the salt has been subjected to flow, 

 the direction of which has not coincided with the original 

 bedding. The gypsum is believed to be a secondary mineral 

 formed by the reaction of calcareous material in the adjacent 

 sediments with the sulphuric acid formed by the decomposi- 

 tion of iron sulphides within the salt formation. 



In a discussion of the origin of asbestos and asbestiform 

 minerals S. Taber (Trans. Amer. Inst. Min. Eng., 191 8, 57, 62- 

 98) comes to the conclusion that the fibrous nature of these 

 minerals is due to the accentuation of a normal prismatic habit, 

 through the limitation of crystal growth by physical condi- 

 tions. 



The following are important recent references upon economic 

 geology : 



Cooke, H. C, Origin of the Gold Deposits of Matachewan District, Northern 



Ontario, Econ. GeoL, 191 9, 14, 281-301. 

 Chlebnikow, K. Ch., Die Manganerzlagerstatten der Ukraine, Zeitsch.f. Prakt. 



Geo/., 191 8, 89-92 ; 100-7. 

 Harder, E. C, Manganiferous Iron Ores of the Cuyuna District, Minnesota, 



Trans. Amer. Inst. Min. Eng., 191 8, 58, 453-86. 



