32 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 5, 



3. Chi the Geology of a part of the Mastjlipatam District. 

 By Captain F. Applegath, Madras Army. 



[Communicated by the President.] 

 (Abridged.) 



The country west of the Palair River, and north of the Kistnah 

 River, is covered with a thinly stratified limestone (E) of a dark blue 

 or black colour, which is about 150 feet thick, and alternates some- 

 times with dark purple slates (A), sometimes with a lighter-coloured 

 speckled slate, and occasionally with some cubical pieces of clay iron- 

 stone. The extent of this district is 24 square miles*. The lime- 

 stone here has a strike due north, and a dip about 19° east : this 

 description mainly applies to all the limestone west of the Palair 

 Eiver. The slates are considered old, and have attracted much 

 attention at Madras. No quarries have been opened in these lime- 

 stone-fields ; but the stone is burnt for lime by the natives, who use 

 the slates extensively for the floors of their houses and verandahs. 

 The slabs are usually about 6 feet long, ?>\ feet wide, and from 2 to 

 8 inches thick. 



The dark-coloured limestone contains casts of shells, and rings 

 when struck by a hammer. A similar limestone in appearance at 

 Kurnool, Province of Ballaghaut, on the Toombuddra River, 250 

 miles N.W. of Madras, contains large quantities of lead ; and in 

 every ton of lead there are 400 oz. of pure silver ; at least, a speci- 

 men analysed showed this per-centage. 



The limestones on the east side of the Palair differ much in colour, 

 appearance, and position from those on the west side, indicating- 

 great disturbance of strata ; they are principally of a pale yellow, 

 salmon, or red colour, sometimes brown, and occasionally black or 

 blue ; they are very thinly stratified, and feather out. The general 

 strike of the yellow limestone is 70° N.E. ; the dip varies from 11° 

 to 30° S. The strike of the dark blue or black limestone here is 

 E., and the dip N". 



The black limestone alternates with red schist, which is found on 

 undulating hills, which are frequently covered by rounded, quartzose 

 pebbles, and occasionally by small masses of clay-ironstone. Each 

 red-schist hill seems an independent basin, as the strata on the top 

 are vertical, and those on the lower portions of the hill dip from 

 20° to 40° towards the centre. There is an evident intrusion of the 

 same igneous rock as that which extends from the banks of the 

 Kistnah for almost two and a half miles in a north-easterly direc- 

 tion. This intrusion appears to divide the red- schist area into two 

 parts ; and the red schist is finally overlain by a long ridge of varie- 

 gated schist, which extends, from the Kistnah banks, in a due 

 northerly direction, for five miles. This schist attains an elevation 

 of 400 feet above the river-bed, being most probably the last deposit ; 

 it has a uniform N.E. strike, and the dip varies from 15° to 50°. 



* A sketch-map and several sections illustrating this paper are deposited in the 

 Society's library. 



