270 Mr Harclie on the Geology oj the 



nic remains having been found in kunkur, nor have I myself 

 been able to detect any decided traces of such bodies. On this 

 subject Mr Benson has remarked : *' In the course of my re- 

 searches in the Gangetic tract, I have never yet met with any 

 fossil shells but those which are still to be found in the rivers, or 

 feeding on the shrubs of their banks ; these I have sometimes 

 found incrusted or filled up with calc-tufF, which is forming 

 every day in the streams *.*" Mr Benson, whose conchological 

 labours have been attended with such happy results, has had 

 every opportunity of ascertaining the fact, and, as far as my 

 experience goes, his remark may be extended to Me war. I 

 have in many situations found species of Planorbes, Uniones, 

 &c. in the soils reposing on the kunkur, but never in the kun- 

 kur itself. We must not, however, infer from the above obser- 

 vations, ihe total absence of organic remains in the kunkur. 

 Future research may probably bring many to light. At the 

 same time, the great apparent scarcity of such bodies is a sin- 

 gular feature in the natural history of this formation, and one 

 which ought not to be passed over in silence in a communication 

 of this nature. 



In its composition, kunkur varies considerably in different 

 situations. This diversity, however, may be attributed more to 

 the nature and kind of its foreign ingredients, than to any irre- 

 gularity in the chemical constitution of the cementing medium. 

 When these ingredients have been reduced to a very fine state 

 of comminution, they are so incorporated with the mass, that it 

 presents the form of a homogeneous substance of a harder or 

 softer nature, according to the nature of the fragmentary parti- 

 cles. The purer varieties are burned for lime, which forms an 

 excellent mortar for ordinary purposes ; though, for finer work, 

 the lime {chunam) prepared from marble or compact limestone 

 is alone used. 



In kunkur, a large proportion of silica and alumina is uni- 

 formly associated with the earthy carbonates, which seldom ex- 

 ist in larger proportion than 60 or 70 per cent, and generally in 

 a still smaller proportion. Oxide of iron is invariably present, 

 and traces of manganese I have also detected ; but the charac- 

 teristic feature in the composition of kunkur is the uniform pre- 

 • See GleaninfTS in Science (Calcutta), vol. i. p. 203. 



