10 6 ON THE CONVOLUTIONS OF STRATA, 



Their positions, and bounding lines, which are very irregular, 

 are laid down, as nearly as we could guess, in the map of 

 the stewartry of Kirkcudbright, now on the table. There is 

 good reason, I conceive^ to suppose, that all granitic masses 

 are related in a similar manner to the neighbouring strata, 

 where such strata are found penetrated by granitic veins. 

 Such veins were first observed, I believe, by M. de Saus- 

 sure, in the Valoisine, and also at Lyons and Semur. Dr 

 Hutton examined them with great care in Glentilt, in 

 Arran, and in other parts of Scotland, and upon these obser- 

 vations founded his bold and original theory with respect to 

 granite. Mr Playfair has not failed to make ample use of 

 those which he has more recently discovered at St Michael's 

 Mount in Cornwall. All the appearances which I have wit- 

 nessed in Galloway, as to the relative situation of granite, and 

 the contiguous rock, accord with the doctrine of Dr Hutton, 

 and tend, I conceive, to confirm his views. 



It might be rash to extend universally to all granite those 

 conclusions which have been established by particular obser- 

 vations ; yet as no instance warranting a contrary inference 

 has occurred since the subject began to be inquired into, 

 enough seems to have been done to contradict the generality 

 of that leading maxim of the Wernerian doctrine, that the 

 order of position which rocks maintain with respect to the 

 centre of the earth, denotes the order of formation. 



It is an important circumstance to observe, that the sub- 

 stance whose formation is thus proved to be prior to that of 

 the granite of Galloway, is the killas, or grauwacke of the 

 German school, which, holding only a middle station among 

 stratified bodies, as to antiquity, is considered, according to 

 their doctrines, or of formation long subsequent to that of 

 any kind of granite. The quality of this stratified mass, 



from 



