MODE XVI. SIDEEOUS GLUTENITE. 137 



the circumjacent sand also arising from the de- 

 composition of the cement. 



Mountains or regions of real glutenite often, 

 however, accompany the skirts of extensive 

 chains of mountains, as on the north-west and 

 south-east sides of the Grampian mountains in 

 Scotland, in which instance the cement is affirm- 

 ed by many travellers to be ferruginous, or some- 

 times argillaceous. The largeness or minuteness 

 of the pebbles or particles cannot be said to alter 

 the nature of the substance ; so that a fine sand- 

 stone is also a glutenite, if viewed by the mi- 

 croscope. They may be divided into two struc- 

 tures : the large-grained, comprising bricias and 

 pudding-stones ; and the small-grained, or sand- 

 stones. 



STRUCTURE I. LARGE-GRAINED GLUTENITES. 



Siderous glutenite, or pudding-stone, from Dun- 

 stafnage, in Scotland, where it forms romantic 

 rocks of a singularly abrupt appearance, in some 

 parts resembling walls. The kernels consist of 

 white quartz, with green or black trap, porphyries, 

 and basaltins. 



Glutenite, from the south of the Grampians, 

 from Ayrshire, from Inglestone bridge, on the 

 road between Edinburgh and Lanark. But of 



