tin iSj 



.t infrequently distinguished by their continuity. 

 A IK-II of limestone has been traced through the heart of 

 the schistose rocks of the Scottish Highland* for s 

 distance of too miles, and similar (probably the same) 

 rocks are prolonged into the west of Ireland a distance 

 of more than soo miles fart: 



Each district must be judged of by itself, and according 

 to hs local peculiarities will be the choke of sones by 

 the geologist He will endeavour to ascertain in what 

 order the different varieties of rock appear to succeed 

 each other, whether or not, in any continuous section, he 

 can determine a true chronological order of succession 

 among them, and whether, if such an order can be made 

 out in one place, it can be extended to others. 



3. Apart from the constant variations in the litho 

 logical nature of the rocks, it is desirable to note the 

 character and strike of the foliation. Over large tracts 

 of the Highlands of Scotland, the direction of the folia- 

 tion of the schists is as persistent, constant, and easily 

 traced as the strike of any series of sedimentary forma- 

 tions. 



In some regions, there can be no doubt that the 

 foliation coincides on the whole with the original bedding. 

 If, for example, we find that, parallel with the planes of 

 foliation, bands of totally distinct mineral character 

 :.ite with each other, such as phyllite, quaruitc, 

 schistose conglomerate, and crystalline limestone, we 

 may with some confidence infer that these bands, though 

 now more or less crystalline and schistose, represent 

 original distinct bands of sedimentary material In many 

 districts, though we may be tolerably certain that the 



