

BUTE. GEOLOGY. 453 



and general characters of these strata are for the same 

 reason equally unnecessary. 



But in mentioning the dip of the schistose strata, the 

 question will naturally arise, by what criterion the strati- 

 fication is distinguished; since, as I have formerly re- 

 marked, there is often a difficulty in discriminating between 

 the schistose lamina and the stratum. As this ques- 

 tion is however discussed at some length in the account 

 of the Isle of Man, I shall here simply describe the 

 circumstance by which the stratification can be deter- 

 mined in this place ; when it will be seen to coincide 

 with the schistose tendency. It is the same criterion 

 by which the opposed position of these two is proved 

 in the island just mentioned, namely, the alternation of 

 substances ; which here takes place in a direction parallel 

 to the schistose lamina, whereas, in that island, it is found 

 in positions variously transverse. The several substances 

 will be particularized in the course of the description. 



It will be remembered that in describing the schistose 

 rocks of Arran, it was found necessary to refer to this 

 island for a fuller explanation of many circumstances 

 relating to them, which their condition in that spot af- 

 forded no means of understanding. The same difficulty 

 exists in a less degree, even in Bute ; although the posi- 

 tion of the rocks is here consistent with that which they 

 maintain on the mainland, and not, as in Arran, per- 

 verted by. the intrusion of granite. The obscurity in this 

 case arises from the great number of substances which occur 

 among the schistose strata, and from the gradation and 

 intermixture that take place among them ; in consequence 

 of which it becomes difficult, if not impossible, to ascer- 

 tain their true relations to each other. This difficulty 

 js increased by the narrow limits of the space which 

 they occupy ; since that which appears to be confusion 

 when it is supposed to be partial, becomes a system of 

 order when found to prevail as a general characteristic, 

 and to extend over a large space. It will indeed be seen, 



