60 On the Advancement of Geological Science in India. [Jam, 



bably made use of the term in its generic sense, following Dr. Mac- 

 culloch ; but the truth is, that hornblende slate is almost un- 

 known in the district of Salem : but had a description of the mi- 

 neral been appended, we should have been led into no mistake.* 

 Observers therefore should in future be careful to append mineralo- 

 gical descriptions of the rocks to which they allude, or at least 

 to make accurate references to mineralogical works, where the des;'rip- 

 tioQ of the characters agree. An attempt is sometimes made to shew 

 that this attention to mineralogical minutiae is not necessary, or to assert 

 that the name of a mineral or rock, sometimes depends on its geological 

 position; but this can never stand good : we cannot make a sheep into a 

 horse, by putting it into a stable ; and many cultivators of science may 

 be sceptical on what are called " the principles of geology," or even 

 deny the dogmas of theorists altogether. Dr. Boase remarks " II a 

 " rock be designated according to its geological relations, its name 

 " must be liable to change, because the principles of the science are 

 " not, as yet, permanently established: besides, on this plan, in the 

 " examination of countries previously unexplored, too much depends 

 *' on the correct judgment of the observer: but when a rock acquires a 

 *' name, from the nature of its composition, whether purely mineralo^iical 

 " or blended with organic remains, then this part of the science becomes 

 ** perfectly descriptive, like the other branches of natural history; and 

 ** much curious and accurate information may then be expected froca 

 *' travellers, who are not accomplished geologists." 



Another common error with observers, is the application of the mine- 

 ralogical name of a rock, to many of the varieties which are interme- 

 diate between it and some other mineral: this should carefully be 

 avoided, and the typical specimens of the rock, having been once des- 

 cribed, its varieties when mentioned should bo named " varieties." 



Another error is the abuse of the term " decomposition" — every rock 

 which is soft or friable, is called decomposed, very often without the 

 slightest proof. The chalk of England is soft enough, but not 1 believe 

 considered generally as decomposed. It is common to call the Indian 

 cotton or regur soil, " decomposed" from trap rocks. It resembles in 

 some measure the lias clay of Dorsetshire, as far as my memory can 

 carry me, but 1 believe the lias of England was never called decom- 

 posed. It is common in India to find 6ssile, friable, gneiss embedding 

 round blocks of granite, and this gneiss has been termed ** decom- 



* I am concerned to hear, that this talented officer, Dr. Benza, who must be consider- 

 ed as having led the way, in first drawing atteution to the geological examination of the 

 South India, is now no more. 



