214 CRETACEOUS ROCKS OF S. INDIA. [PaRT III. 



bed being traced in the interval. These flints are used by the natives 

 of the surrounding villages for obtaining fire with a steel. They are 

 not well seen in situ, but as I have never met with anything like a con- 

 cretionary nodule, such as occur in the chalk of Europe, but only irre- 

 gular fragments, I am inclined to believe that they form a continuous 

 band now more or less shattered. 



I have mentioned before the occurrence at Trivandipuram of yellow 



ochre, which is used by the natives for making 

 Ochre. 



their caste marks. When ground and laevigated, 



it yields a very good pigment. The chatty clay of Terany treated in 



the same way yields a deep red pigment. 



Gypsum. This mineral is common in many parts of the Cretaceous 



rocks of Trichinopoly ; generally in the form of 

 Gypsum, 



fibrous plates intercalated in the bedding, and of no 



great thickness : more rarely in concretions, and replacing the shells of 

 Nautili, Ammonites, and other fossils. 1 have nowhere seen a pure 

 gypsum fitted for the preparation of stucco or statuary casts, as it almost 

 invariably contains a small proportion of clay, which cannot be separated 

 by washing, and which would destroy its whiteness ; but it may be obtain- 

 ed, in any desired quantity, of sufficient purity for the preparation of 

 moulds, such as are used in the ceramic arts, or indeed for any purpose 

 in which pure whiteness is not essential. It is most abundant in the 

 Ootatoor beds, especially in the Belemnite clays to the East of Ootatoor, 

 and in the unfossiliferous clay to the North-east of Maravuttoor. At the 

 former place it occurs in fibrous plates of from half an inch to 2 or 3 

 inches in thickness, and may be collected in any quantity in the broken 

 o-round between Ootatoor and Garoodamungalum. At Maravuttoor it 

 occurs both in the fibrous form, and in transparent plates, (Selenite) 

 and crystals irregularly intercalated in the clays of the lower part of 

 the group. Fragments of great purity may be easily selected, but it 

 cannot be obtained in any quantity free from the argillaceous matrix. 



