9,38 Dr Hibbert on the Limestone of Burdiehouse, 



Section from Morton (at the foot of the Pentland and Braid Hills) to Stobhill, 



NW. by W. to SE. by S. 



NW. by W. SE. by E. 



£ Grace- Roman 



S mount Mount. 



H System. Burdiehouse System. Hawthornden System. Stobhill System. 



One Mile. 



In reference to this section, it will appear that I have dis- 

 tinguished four systems of strata, divided from each other by 

 lines of fissure, viz. the Gracemount, the Burdiehouse, the Haw- 

 thornden, and the Stobhill systems. 



In giving a very brief explanation of these various systems, I 

 shall commence with the Hawthornden system, notwithstanding 

 the greater degree of obscurity which still hangs over it, in refe- 

 rence to the question, long since agitated, regarding its geological 

 position. 



The Hawthornden system comprises a peculiar thick bed of 

 reddish and softish sandstone, in which small rounded pebbles of 

 quartz are inclosed. It is geologically known by the name of the 

 Roslin sandstone. This sandstone, which, from its quartzose in- 

 gredients and other circumstances, appears to me to have been de- 

 posited soon after the formation of transition rocks, may have un- 

 dergone an earlier elevation than perhaps any other strata be- 

 longing to the systems which are laid down. The consequence of 

 this priority of elevation may have been that want of continuity 

 which the coal strata superimposed upon the Roslin sandstone 

 exhibit, in relation to other coal seams lying to the west and 

 east of them ; although, from a mineralogical correspondence, 

 their relative date may perhaps be correctly estimated. The 

 thick bed of Roslin sandstone, which is surmounted by eight or 

 more conformable seams of coal, exhibits a very trifling dip of 

 10° or 12° to the east or north-east. It is separated from the 

 highly inclined strata of the Loanhead coal-measure, belonging 



