Revieivs — Petroleum in Assam and Bengal. 377 



decomposition products, quartz and olivine may be found in the same 

 rock. Mr. N. L. Bowen discusses crystallization - differentiation in 

 silicate liquids and shows experimentally that crystals sink with 

 considerable rapidity in artificial melts. Hence this process may be 

 of importance in the differentiation of igneous magmas. — R. H. Pi. 



Y. — The Petroleum Occurrences of Assam and Bengal. By E. H. 

 Pascoe, M.A., D.Sc. Mem. Geol. Surv. India, vol. xl, pt. ii. 



f PHE present volume forms a fitting sequel to the author's recent 

 _L work on the Oil-fields of Burma, which has made Further 

 Indian oil-fields better understood than many of those in Europe and 

 America. 



The Coal-measures series in which the oil occurs is almost certainly 

 the homotaxial equivalent of the Pegu Beds of Burma. They are 

 underlain by the Nummulitic Series, while the overlying Tipam 

 Sandstones are very similar to the Irrawadi Beds. It would appear 

 that whereas the Burma oil-fields occur in the Hinterland behind the 

 region of maximum mountain-building movement, those of Assam 

 form a belt in the Forland a little to the west of the great boundary 

 thrust, and have suffered more intense folding. The author infers 

 overfolding in each of the main oil-fields, and although the poor 

 exposures and dense forest render the matter difficult of proof, the 

 balance of evidence appears to favour this view. The folding is 

 probably accompanied by thrusting, and the structures produced are 

 very similar to those of some of the Carpathian oil-fields. 



Another point of interest is the supposed interference of the 

 Himalayan and Burmese movements in the north -eastern portion of 

 the area. The close association of oil and coal, and the sparsity of 

 animal remains, certainly support the views of the geologists of 

 Burma, that in these beds of Further India the natural hydrocarbons 

 are mainly of vegetable origin. 



VI. — Brief Notices. 



1. Eaethquakes in Burma. — In the month of May, 1912, Burma 

 was visited by severe earthquakes, which culminated in a great shock 

 on the morning of May 23. This was sensible over an area of 

 375,000 square miles, and caused much damage in Mandalay, 

 Maymyo, and other places, though attended by little or no loss 

 of life, owing to the character of the buildings. This shock is 

 described in detail by Mr. J. Coggin Brown (Mem. Geol. Surv. India, 

 vol. xlii, pt. i). In the central part of the area the shock reached 

 the intensity of ix on the Bossi-Forel scale, although this isoseist 

 could not be exactly delimited; the other isoseists had an elliptical 

 form, with their long axes running north and south. The position of 

 this long axis coincided very nearly with the great Kyaukkyan fault, 

 described by Mr. La Touche as one of the most notable features of 

 Burmese geology ; the railway was bent where it crosses this fault, 

 but unaffected where it crosses the other faults of the plateau. No 

 actual surface displacement was anywhere observed. 



