78 



three belong to one period of disturbance tbat they were simulta- 

 neously injected amid the rocks which now enclose them, at a period 

 subsequent to the deposit of the carboniferous strata? But the 

 evidence for this conclusion is incomplete without a decided example, 

 along the line of junction of the coarse and fine varieties in the inte- 

 rior, of veins from the latter penetrating the former. Such a case 

 has never been seen by us, or recorded by any observer, as already 

 noticed (Art. 46, p. 68). Its discovery would amply repay the 

 trouble of a careful search, and render much more probable the pos- 

 teriority of the fine variety. Much also depends on the view which 

 may be taken respecting the rounded pieces of fine grained granite 

 enclosed in the conglomerate, close to the Craig-Dhu granite (Art. 

 51). If our explanation of their occurrence there be deemed unsatis- 

 factory, then will not the above conclusion hold ; and it must be 

 admitted that, before the irruption of the Craig-Dhu granite, the 

 fine grained variety of the interior must have been elevated, stript of 

 its slate covering, and exposed to degradation. 



54. What, then, it may be asked, is the conclusion which we 

 favour, and to be finally drawn from these various and somewhat 

 conflicting statements ? The discussion may seem tedious and unim- 

 portant to many ; yet we hope it will not be without its use to the 

 student and future inquirer ; and as several of the facts are new, it 

 may have some value in the eyes of the many geologists in this and 

 other countries, who have either written upon the subject or take a 

 lively interest in the physical history of this extraordinary island. 

 The question of relative age is, we hope, much narrowed by these 

 statements, but for the present must remain unsettled. The various 

 possible conclusions may be set forth, by way of recapitulation, as 

 follows : 



1 . The oldest rock in the island is the slate. 



2. The old red sandstone and the carboniferous sandstones, with 

 their intercalated limestones and coal strata, were formed before the 

 granite was exposed to disintegration, the only fragments of this 

 rock yet found being those in close proximity to the Craig-Dhu mass, 

 of which they are probably injected pieces, and not derived from the 

 disintegration of a granite already exposed. 



3. The injection of the granite of the nucleus, that is the coarse 

 grained or Goatfell granite, in a molten state, amid the slate strata, 

 was certainly posterior to the deposit of the old red sandstone, and 

 may have been posterior also to that of the carboniferous strata. 



4. If the granite of the nucleus be thus of later age than the car- 

 boniferous strata, then may ah 1 the three granites be of one age, such 



