MANUAL OF THE NJLAGIRI DISTRICT. 83 



CHAPTER V. 



GEOLOGY AND MINERALOGY. 



Geology and 



ERALOGY. 



Early papers. — Geological Survey. — General desci'iption. — Action of water — fre.sh 

 — marine. — Rock formation. — Granite absent.— Gaeissose rocks — foliations. — 

 Minerals — iron — horublendic gneiss. — Other varieties — Land.slips. — Intruded 

 rocks. — Dislocations. — Three systems of faults. — Disturbances. — Upheaval 

 of the ghdts. — Quartz veins. — Withering of rocks. — Laterite. — Kaolin.— 

 Clays. — Escarpments. — Kaity valley. — Kundas. — ^ Alluvial. — Economic geology. 

 — Limestone. — Mr. King's note. — Gold. — Sonth-East Wainid. 



Several papers on the geological and mineralogical structure of CHAP. v 

 these hills have, from time to time during the last forty years 

 been laid before the public. The earliest of these was a '' Geolo- min 



gical Sketch of the Nilgiris/^ contributed to the Journal of the 



Asiatic Society of Bengal in 1835 by Dr. P. M. deBenza, the 

 Surgeon to the Governor of Madras at the time. This paper, 

 which is spoken of by Mr, Blandford as " very excellent/' will 

 be found in an improved form in Volume III of the Journal of the 

 Madras Literary and Scientific Society. " The Eeport on the 

 Medical Topography of the Neilgherry Hills/' printed by order 

 of Government in 1844, contains some valuable remarks on the 

 geology of the hills. During this and the following year a 

 series of letters on their topography, geology, and ethnology 

 was contributed to the Madras Spectator by Captain Congreve 

 and Dr. Burrell. Later, Captain Congreve, in the year 1861 

 (Vol. V, No. XVI, December) furnished another paper on the 

 geology of the district to the Madras Literary and Scientific 

 Society, in which his opinions and observations are given in 

 a more systematic form than in the earlier brochures. In 

 Major Ouchterlony's Survey Memoir (1847) there will also be 

 found some information on the subject, as also in two papers 

 contributed to the Journal of the Asiatic Society, Bengal, New 

 Series, No. LXXXVI, about the year 1856. 



