Dec. 1861.] Geology of the Neilgherries. 243 



(e.) In masses dispersed over the surface, and consisting of 

 aggregated crystals. 



From these effects I induce the following history of this ore. 



(a.) First a vein of iron came to the surface through the body 

 of the Hill, and overran the rocks upon it. 



(b.) It percolated through the pores of the decaying rock and 

 crystallized into iron mica. 



(c.) Where fissures existed in the rock the iron formed veins. 



(d.) Overflowing the surface of the Hill the metal ran down 

 its sides in thin streams, and lastly. 



(e.) In concavities of the surface the molten iron settled, and 

 by the process of slow cooling crystallized. 



The soil having subsequently degraded from around the masses 

 of the metal, left them exposed on the surface. 



Some of the out lying fragments of the ore contain cells lined 

 with crystals of quartz. 



Pieces of the ore also occur with botry oidal surfaces, hollow in- 

 side ; these have been evidently crusts of a rock which has disinte- 

 grated from beneath them. 



Oxydulous Iron (native loadstone) some pieces powerful enough 

 to raise a needle, and Ferruginous quartz are associated with this 

 ore, of which I now annex a mineralogical definition. 



Regularly Crystallised Iron Glance, which Griffin includes un- 

 der the head of red Hcematite, Phillips separates one from the 

 other, and calls the ore Specular iron specific gravity 4"28 which is 

 0'72 under that of Elba, a discrepancy arising I conjecture from 

 the number of cells in the Neilgherry ore filled with earthy matter. 



Primary Crystal. — Acute rhomboid. Hardness — between quartz 

 and Felspar. Streak red. Chemical analysis proves it to be a 

 peroxide. Magnet acts on its dust. Color — dark steel grey. 

 Lustre highly metallic, and sometimes tarnished. 



The Hill on which the above ore occurs, is separated from the 

 North West flank of Dodabett by a stream and road. 



In the surface of the latter, Doctor Burrell found the same 



