Mtirchisons Silurian System. 539 



learnt from Mr. Murchison that it reposes beneath the lime- 

 stone of the coal measures, and that the only fossil yet dis- 

 covered in it is the scale of a fish, already alluded to. 



The uncertainty connected with the relative position of 

 rocks in districts not regularly investigated, must expose all 

 casual observations on the identity of structure in remote 

 situations on the earth's surface to serious difficulties. 



To compare one district, the peculiarities of which have 

 been thoroughly investigated with another but partially 

 known, in a remote part of the world, we have not only to 

 be on our guard against various forms which the same rocks 

 are liable to assume under different circumstances, but we 

 have also to recollect that the laws of geographical dis- 

 tribution of animals should prevent our expecting to find 

 the same organic remains every where in the same rock. 



In the first reports of the Coal Committee we stated our 

 reasons for regarding the beds of sandstone which form the 

 basis of the coal measures at Cherra Ponji as equivalent 

 to the old red sandstone. The relative position of the beds 

 in question to the coal formation, as well their position and 

 lithological characters as far as we are acquainted with them, 

 are all in favour of their belonging to the upper group of the 

 old red sandstone, which formation, according to observa- 

 tions of Mr. W. Jameson not yet fully before the public, is 

 largely developed in the North-western parts of India. 



There is really nothing in the name that ought to deter 

 us from using it to designate a formation agreeing at least in 

 all its main characters with the English rock, and occupy- 

 ing the same relative position between the coal measures on 

 the one side, and the more ancient rocks on the other. 



Thus the vast extent to which the old red sandstone 

 occurs in India is the best proof of the importance of the 

 subject to the Indian geologist, and of the necessity of his 

 being in full possession of all the particulars brought for- 

 ward by Mr. Murchison in his valuable work. Our review 



4 A 



