OF CENTRAL INDIA AND BENGAL. 301 



Granting even that the remains of organized existence thus found 

 entombed at opposite sides of the globe are truly identical, would 

 this identity prove such a synchronism in the period of the forma- 

 tion of the rocks as to warrant the application of a classification 

 founded on facts observed in far distant lands ? Or if we go further and 

 grant that the species although not identical may be representative, can 

 we assert that this fact can be taken as evidence of synchronism ? And 

 we must also remember the important fact first distinctly announced by 

 Edward Forbes, that these species or forms, which are thus widely 

 spread in space, are precisely those which are most widely spread in 

 time, and are therefore of the least use as evidence of contemporaneity 

 of the beds in which they occur. Under this point of view, it is to 

 every one who looks to the grand generalizations of the geologist, a 

 matter of the most intense interest to establish the true correlation of 

 any given series of rocks in tropical regions with any established group 

 in Europe, and to trace out the differences both in petrological character, 

 and in organic remains, which may coexist with a general resemblance 

 or conformity to an admitted type. From the first commencement of 

 our labors in Bengal, therefore, it has been a steadily pursued object of 

 my wishes, to establish the age of some fixed group of rocks, and thus to 

 determine a definite horizon, or datum line, from which we could either 

 work upwards to more recent deposits, or downwards to more ancient 

 systems. There were many and very conclusive reasons, besides these 

 general considerations, why, if it were possible, the age of the coal- 

 bearing rocks of Bengal, and Central-India should be the first determin- 

 ed. They were, unavoidably, the first to which we were obliged to 

 direct our attention ; they were of great thickness, and covered a very 

 large and widely extended area; and they were commercially and eco- 

 nomically of infinitely greater importance than other groups. I have 

 therefore steadily kept before me this object, as has been proved by 

 every brief notice which from time to time I published concerning these 

 rocks. 



