cciv Journal of the Asiat. Soc. of Bengal. [N.S., XIII, 1917.] 



compared with those of augite, and the presence of felspar microlites in 

 the groundmass. Si(>2 = 40*73 per cent. According to the M Quantita- 

 tive Classification " the position of the rock is III. 6. 4. 4, and the term 

 Hamandunose has heen proposed for the subrang. The presence of felspar 

 in the groundmass is discussed and it is suggested that a very large sec- 

 tion of the rocks now known as limburgites is very closely allied to the 

 picrites. 



Corundum and its Occurrence in Mysore. — By L. Subba Rao. 



After a brief reference to the origin of the word corundum, the author 

 proceeds to describe the economic value of the mineral and states that, 

 though corundum is the richest and purest of the ores of aluminium, the 

 cost of the mineral compared with that of Bauxite presents a real 

 difficulty in the way of using the former for the manufacture of the 

 metal. The paper then goes on to describe the crystalline form of the 

 mineral. Three twinned crystals are described as specially deserving of 

 mention. Two of them are of the cruciform type and the third repre- 

 sents prism of the second order and rhombohedron combined on the 

 prism of the first order as the composition plane, the twin thus giving 

 rise to a curious monoclinic appearance. The paper then refers to 

 certain samples of corundum occurring at Kupya and Doddrei in Mysore 

 where this mineral, which is generally considered unalterable, is found to 

 be surrounded by a greenish material which the author makes out to be 

 marganle. The author discusses the nature of this alteration and cites 

 Professor Judd's statement that conditions must exist in the earth's 

 interior under which chemical change of this mineral does take place. 



in Mysore. After stating that mineralogically emery is simply a mixture 

 of corundum and magnetite and that its value as an abrading agent 

 depends upon the proportion of the former constituent, the author men- 

 tions a locality ,n Mysore where corundom crystals are found enclosing 

 grams ot magnetite arranged in peculiar patterns as stellate figures, etc. 

 ano gives it as hia opinion that such occurrences are to be considered as 

 merely instances of emery. 



»* . Th ® P a P er concludes "with a short note on the origin of corundum and 

 scares that its occurrence in Mysore well illustrates the processes of 

 mKSi metamorphism. In many cases, says the author, it is of 

 S° ub S ly - meta morphic origin and in others it is the direct result, in 

 piace, ot basic igneous masses. According to the author, the corundum 

 whinf Pr , ov,nce ^n be divided into two main groups :-(l) those in 

 m,iS,- " m IS as 'l ociated with basic rocks intruding into the sur- 



fnSS S ? ei fu eS a £ d (2) those in which jt » associated with acid rocks 

 \ vsZ H ! °S er ara P hi bolites ; and examples are given from 



Mysore Province to illustrate each tvpe of occurrence. 



Lectures. 



Three public lectures were delivered : 



cc mi r** 



« Si 6 8n Kv~: By C> MlCHIE 8mit h, Esq., CLE., B.Sc. 

 Soanng Flight » -ty Dr . E. H. Hankin. 



Explosives \- By F. L. Usher, Esq., B.Sc. 



LibrorL^nXS^fr^ 88 a ? eneral discussion on « Scientific 



F.R.S.. e fntUtrr.w W hton 0l S S T ^ BmV ^ ^-CSJ., R-E-, 

 on "The Future of thl i °? th ® last afternoon there was a discussion 

 President. le Ind,an Scienpe Congress " presided over by the 



