268 Revieivs — Mineral Products of India. 



A final cliapter treats of tlie tectonic structure of the district and 

 the possibility of the Eocene rocks and the jS'ubian Sandstone having 

 had formerly a wider extension. In summarizing the past history of 

 this part of Africa Dr. Ball suggests that the Red Sea depression 

 originated between Upper Cretaceous and Oligocene times, and was 

 increased in area by a- sinking of the crust along its margin in 

 Miocene times. The main drainage systems were, he thinks, initiated 

 as early as the Oligocene period. 



H. G. L. 



III. — Geological Survey : Mineral Pkodccts of India. 



A REVIEW of the mineral production of India during the year 1911 

 xJL is given by the Director, Mr. H. H. Hayden, in pt. iii of vol. xlii 

 of the Records. The method of classification is the same as that used 

 previously, and we learn tliat the collecting of returns becomes more 

 precise every year. A comparison of the total value of the minerals 

 produced in 1910 and in 1911 shows an insignificant fall of half per 

 cent. At the same time such important minerals as coal, gold, 

 petroleum, and wolfram show a steady rise, the drop in the value of 

 the total production being due to the curtailment in the output of 

 manganese. The paper gives full tabular details of the mineral 

 concessions granted during the year, and these show a good increase, 

 this being due chiefly to the quest for wolfram in Lower Burma and 

 for manganese in the Central Provinces. 



The second paper in this part is by Dr. L. L. Fermor on " The 

 Systematic Position of the Kodurite Series, especially with reference 

 to the Quantitative Classification ". Some three years ago Dr. Fermor 

 described the series of rocks of which kodurite (composed of orthoclase 

 felspar, a manganese garnet and apatite) is the type, but at the time he 

 was unable to investigate its classificatory position. He has lately 

 been able to investigate the matter, and has taken the opportunity of 

 testing the methods of quantitative classification as set forth by 

 Messrs. Cross, Iddings, Pirsson, and Washington. Dr. Fermor finds 

 that tliese methods lack elasticity ; on the other hand, he found no 

 difficulty in fitting the kodurites in the classification adopted by 

 Hatch, in which the Kotakarra kodurite may be called a mangan- 

 shonkinite. One of the difficulties in the American system is the 

 inability to deal with high MnO. The author finds the 'norm' 

 distinctly useful, however, and promises further discussion on this 

 point Avhen his investigations are complete. 



IV. — Indian Desert Salt Deposits. 



IN an interesting and highly important article on " The Origin 

 of Desert Salt Deposits " Professor Sir Thomas H. Holland 

 gives the results of his researches, aided by chemical analyses made 

 by Dr. W. A. K. Christie, on the salt deposits of the Rajputana 

 Desert (Proc. Liverpool Geol. Soc, xi, p. 227, 1912). It is pointed 

 out that " Throughout the whole desert tlie subsoil water is 



