484 Notes, chiefly Geological, from Goofy to Hydrabad. [May, 



Four or five dykes of basaltic green-stone, or possibly the ramifications 

 of one enormous coulee, traverse the granite rocks of Hydrabad with a 

 general easterly direction. One of them runs through the tombs of 

 the kings at Golconda, and is probably identical with that seen six 

 miles to the eastward between the British Residency and the great tank 

 of Hussain Saugor. From the blasted and chiselled appearance of 

 some of the blocks and mineral resemblance, this dyke has evidently 

 contributed part of the material for the dark and highly polished 

 slabs of which the royal tombs are constructed. It must not be 

 confounded, as has been done by Malcolm son,* with the dark 

 talcose rock of the pillars supporting the tombs of Hyder and 

 Tippoo at Seringapatam . The rock on which stands the celebrated 

 fortress of Golconda is of a granite resembling that of Gooty, with 

 reddish felspar, quartz in small grains, dark dull green scales of mica, 

 and a little hornblende. Actynolite, both crystallized and blended 

 with compact felspar and quartz, occurs in veins pretty generally 

 throughout the granitic rocks of Hydrabad. — A rough trigonometric 

 observation from a paced base makes the rock of Golconda 450 ft. 

 above the general level of the plain. 



Soil. — The surface soil, in the vicinity of Hydrabad, is the reddish, 

 granite alluvium, partly washed down from the sides of the neighbour- 

 ing hills, and partly the debris of the decaying rocks on the spot. It 

 is originally reddish in colour, but often altered by cultivation and 

 manuring into an ashy grey. It generally contains a small proportion 

 of calcarious and saline matter, — derived, probably, from the infiltration 

 of water which has held these minerals in solution. 



The alluvium brought down by the Mussy (here from 100 to 180 

 yards broad), from the westward, is a reddish sand and silt ; also beds 

 of pebbles chiefly granite, nodules of ferruginous clay, (apparently from 

 lateritic beds,) and kunker. 



Voysey states that this river rises in a granitic country, (according to 

 Hamilton, it rises about 43 miles W. from Hydrabad, at the Anantghur 

 pagoda,) and attributes to this cause the circumstance of its not having 

 black alluvium or regur on its banks. (Vide my remarks on the 

 Kistnah in this paper). It may be here stated that the Tumbuddra 



* Madras Journal, July, 1836, p, 199. 



