Reviews — Records of the Geological Survey of India. 129 



fossils (Cambrian) with those of their nearest neighbours of approxi- 

 mately the same age. It is thought that the investigation of these 

 Spiti Cambrians will have an. important bearing on the classification 

 adopted for the oldest Paloeozoic systems of the Himalaya. 



Economics. — Several pages are devoted to this subject under the 

 heading of "Enquiries" and "Surveys". Manganese-ore, with the 

 exception of gold, the only heavy metal of any importance as a product 

 in India, attracts some attention. The chief object of the surveyors 

 latterly has been to institute a comparison between the deposits in 

 South India and those of the Central Provinces. In the latter area 

 the ore-bodies as now constituted appear to be an integral part of the 

 crystalline complex, although it is probable that they have attained 

 their present character of clean oxides by alteration of manganese 

 silicates. In South India, on the other hand, the ore deposits are 

 more superficial, and appear to be residual products from the surface 

 alteration of the "various lithological elements that constitute the 

 Dharwar system of schists". The manganese-ores of this class occur 

 iricgularly associated with lithomarges, ochres, and wads. A com- 

 parison is then instituted between these shallow or surface ore-bodies 

 and those of the crystalline complex. As regards these latter it is 

 hinted that they may be found in depth to pass down into manganese 

 silicates unsuitable for the requirements of the metallurgist. 



In connection with the subject of petroleum in Burma "a survey 

 of the Minbu Hills " may be taken as in some sense typical of the 

 region in the neighbourhood of the oilfield. " This anticline of 

 Miocene and Pliocene beds is one of great interest from a scientific 

 point of view. Slightly asymmetric and sharply folded, it has been 

 very extensively denuded and its deeper structure laid bare. There 

 are many comparatively large faults, one of which appears to coincide 

 with the line of mud volcanoes near the town of Minbu." The 

 results of boring for oil in this particular district ai'e not very 

 encouraging. 



As a further contribution to the economic geology of Burma, there 

 is a note on the occurrence of tin-ore in the Mergui district. The 

 only ore worked is cassiterite, and this occurs as a somewhat scarce 

 constituent in a decomposed pegmatite rich in tourmaline and 

 muscovite, in fact under conditions not dissimilar from those at 

 home. The industry is a small one, the output in 1907 being valued 

 at £11,882. 



Geological Surveys. — In Central India the major portion of the area 

 surveyed in 1907 is occupied by the Deccan Trap, and three thin beds 

 of what appear to be fragmental volcanic ejectamenta were found 

 intercalated with the normal basalts. The lowermost bed of the 

 Deccan Trap occupies the flat plains for several miles before the 

 upper beds composing the scarp make their appearance. The scarped 

 edge of the Malwa plateau rises more than 1,000 feet in softer and 

 harder beds of trap, some of which are columnar, and some contain 

 the usual geodes, full of siliceous or zeolitic material. 



The Northern Shan States of Burma are described with considerable 

 detail, and a graptolite band (Pangh-sapye) in the Upper Ordovician 

 was found to be of considerable service in working out the 



