332 



Granitic Formation of 



[Oct. 



It has been already stated that dislocation has taken place most rea- 

 dily where the fragments are largest, but it is a question by what kind of 

 force this effect has been produced ; whether the impetus has passed along 

 those lines where the fracture is apparent, or, whether the pressure on 

 the surface has been generally distributed — in which latter case the crust 

 might have been expected to give way where there was the least resist- 

 ance. Although it is more likely that expansive force should prevail over 

 a considerable extent at one time, yet it is not clear by what rule the 

 most ponderous and solid fragments should be the most affected by it. 



In instances where hills, or tracts of table-land, have been forced up 

 from the general level, the summit usually corresponds in its superfi- 

 cial crust with the plain from which it has parted, while the escarpment, 

 or intermediate space, is wanting in this crust common to the two proper 

 surfaces. This is seen in the ghaut region, the escarpments, even when 

 not very steep, being deficient in the iron clay and diluvial gravel: the 

 want of these on the fractures, shews the elevation of the hills and 

 table-land, to be a more recent geological event than the deposition of 

 the diluvial gravel. In the Konkan north of Goa the elevation of the 

 ghauts is clearly pointed out as subsequent to the formation of laterite : 

 the table-land is covered with a thick crust of this substance, as well as 

 the lower level of the Konkan : and hills, which appear rising from the 

 low ground as detached portions of the table-land, are flat topped, with 

 a crust of the same laterite, while their slopes, like the general escarp- 

 ment of the ghauts, is covered only with a loose debris. 



It has been remarked that granite in America is found at a much 

 lower level than in Europe : this is also the case throughout the south 

 of India, by granite — meaning always granitic rocks ; for a regularly crys- 

 tallized compound of quartz, felspar and mica is not to be expected.* 

 The Carnatic, and several other similar tracts, occurring along both 

 coasts, are, as granitic plains, surprisingly level : the slight tertiary 

 diluvium with which they are covered, cannot be considered as a prin- 

 cipal cause of this uniformity, for the rock itself is everywhere found 

 near the surface : every appearance here indicates that the granitic 

 formation has at one time been a great deal more fiat than ii is generally 



* The only sure method of identifying one kind of granite with another, is by pre- 

 serving- types or average specimens of each distinct variety for reference : little can be 

 understood by description, and no general rules can be laid down for definition : they do 

 not vary so much in composition as in mode of crystallization and colour.t 



+ The author appears to lay too much stress on the colour, composition and mode of 

 crystallization of rocks, which, without attention to geological position, can only be con- 

 sidered vague and insufficient criteria. So much do hand specimens mislead, that frag- 

 ments of many species of primary granite could not be distinguished, as far as mere 

 external characters go, from the overlying rocks of the trap formation.— Editor. 



