STRATA of the GRAMPIANS. '9 



are of a vaft variety of fize, from that of a pea to the bulk of an 

 oflrich Qgg. Thefe are all firmly combined by an argillaceous 

 ferruginous cement. In fome parts of this gravel rock, are to 

 be feen thin lines of a fine-grained grit, ftretching through it 

 from weft to eaft ; it is by thoie lines alone that the vertica- 

 lity and the ftretch of this mafs is difcoverable. Its general co- 

 lour, in mafs, is that of a ferruginous red. 



This plum-pudding rock is immediately followed by a fuc- 

 ceffion of flrata of fine-grained grit, in thin layers : it has a very 

 considerable degree of induration, and is of a dark ferruginous 

 brown colour. This deviates a little from the vertical pofition, and 

 inclines to the fouth : the ftretch is from weft to eaft, and its ex- 

 tent towards the north is two hundred and fixty yards. To this 

 rock immediately fucceeds a fpecies of Porphyry, the principal 

 mafs of which confifts of an indurated argil. Its colour is of a 

 purple or lilac brown : its induration is very confiderable, and 

 its fracture is rough and earthy. The materials which are im- 

 bedded in its mafs, confift of fmall particles of quartz, felfpar, 

 blackifh-brown mica, and fpecks of iron ochre ; all of thefe are 

 but thinly fcattered. The fpace in the courfe of the river occu- 

 pied by this porphyry is two hundred and twenty yards : its 

 ftretch is nearly from weft to eaft, and it inclines in a fmall de- 

 gree to the fouth. The rock which fucceeds to this porphyry, 

 and which is in contact with it, is difficult to defcribe ; and this 

 difficulty arifes from the great diforder of the ftratification, and 

 the variety of materials compofing it. The ftrata of this bed do 

 not fucceed each other in a regular manner. Portions of them 

 of various dimenfions lie together, but very varioufly difpofed : 

 fome are vertical, fome horizontal, fome dip to the fouth, one 

 only to the north, affording a folitary inftance of a northern in- 

 clination of the ftrata in this field of examination. 



The materials of this mafs of confufed ftratification, are of 

 very different defcriptions. In one place, a quartzofe ftone 



Vol. VI.— P. I. B abounds. 



