296 Journal of the Asiatic Society of Bengal. [N.S., XIII, 



series in the quantitative chemico-mineralogical classification of 

 the American petrographers, 1 nothing has been done to fit any 

 Indian rock into this classificatory scheme. From the mole- 

 cular ratios of the different constituents of the Hamandun rock 

 the following norm has been calculated : 



Orthoclase 



Anorthite 



Nepheline 



Diopside 



Olivine 



Akermanite 



Magnetite 



Tlmenite 



5-56 



3975 



1392 



1558 



12-89 



0-86 



7-89 



1-37 



H 2 



• • 



97-82 

 1-41 



9923 



From the norm given above the position of the rock has 

 determined »« fnii^wo .__. 



been determined as follows : 



Class III Salfemane— Salfemic 

 Order 6 Portugare— Lendofelic. 

 Rang 4 Hamandunase 2 — docalcic. 

 Subrang 4 Hamandunose— presodic. 

 Grad 2 Hamandunate — dopolic 

 Subgrad 1 Hamandunote 



Section 1 

 Subsection 1 



-permirlic. 



premiric. 



premagnesic 



A question has recently arisen about the true nature of 



luZ Z gV T; ^ S ° ri g mall y defined by Rosenbusch the rock is 

 supposed^tobe free from felspar.* * It was Prof. Bonney who 



XLV, i p te ] d 03) ntire man 8 anese -° r e deposits' (Rec. Geol. Sow. Ind., Vol. 



son and" wlshWnn^ 3 p ification of Igneous Rocks by Cross, Iddings, Pirs- 

 GeoL, VoL jJ^SiSfi SIT *°' *' U * Ge ° L ^ "^ J ° Urn " 



docile™ 'JSuL / S5 SC T eme had ori 8»«Wy * threefold division for 

 subsequent^ r^tfi;* uJ- Ign - rocks ' P- 137). This arrangement was 

 and tC find fhe n^TJ^ ^ P No " 28, U.S. Geol. slrv..p. 14), 

 rocks, Vol IlTii t ° tbe 8ymbo1 IIL 6 - 4 - 4 " 5 (Iddings: Igneous 

 4 - 3 (4) (C R aV«h U' t> Lacr °* x Proposed the name Papenooae for III. 6. 

 20, p. 551 I'^f * | r n Pa ,u S * ^° L 15, 'P- '24,1910,and Journ. Geol., Vol. 

 should be Panenoai i f /° 1IoW8 th «t the corresponding rang name 

 culation as the taX L t evidentl y there was some mistake in the cal- 

 name was proposed fiT*? gabbro from Tahiti) for which the above 

 2, 2 (Iddings Tneou " Lf eq ^ e, ? tIy been found ou * to belong to lV ' 2> 

 has been s, JgestS by me '' V ° L "' P ' 653) ' Accordingly a new name 



■ Elemente der Gesteinslehre . p. 861. In the latest edition of • Mikros- 



