548 ISLE OF MAN. GEOLOGY. SANDSTONE. 



the beds of the sandstone. But a great change in the 

 regularity of both, takes place at the points of contact 

 between the two; the schist being much twisted and 

 bent, and the regularity of the sandstone beds being 

 nearly obliterated. Similar confusion occurs in the 

 composition of the substances themselves ; the schist 

 becoming in some cases coarse, and charged with sand, 

 and the sandstone being for a short space so inter- 

 mingled with the argillaceous matter of the schist, as 

 to put on the aspect and character of graywacke. 

 These appearances however, extend on either side, only 

 to a few feet ; but it may also be remarked that the 

 schist acquires a mixture of red in this place, while 

 some parts of the sandstone, on the contrary, become 

 blue. 



The probable causes of this confusion of position 

 and character, which not unfrequently occurs at the 

 junctions of the primary and secondary rocks, have been 

 subjects of discussion among geologists, but no satis- 

 factory explanation of the appearances has yet been 

 given. It may however be remarked that those causes 

 which have been supposed to operate in producing 

 similar effects, where the junction is that of granite 

 or of trap with the stratified rocks, do not seem ap- 

 plicable to the present case; the junction here, being 

 that of the primary with the secondary strata. These 

 disturbances are also more interesting, since they are 

 either of less frequent occurrence, or have been more 

 rarely noticed. In most of the instances which have 

 occurred in my experience in Scotland, such junctions 

 are undisturbed and regular, the secondary rock lying 

 on the primary, either in conformable order or otherwise. 

 One conclusion however may perhaps be drawn from 

 a consideration of the appearances in question. Whether 

 the schist has acquired its present position, either in 

 consequence of elevation or subsidence, it has not only 

 been so disturbed after the deposition of the sandstone, 



