326 Mr. MuRCHisoN on the Coal-field of Brora in Sutherlandshire, ^c. 



Section of the Coal Strata at the Engine Pit, Brora Colliery, by Mr. William 

 Hughes. 1814. Corrected by Robert Bald, Esq. 



Ft. In. 



1. Dark coloured schistose sandstone, 



containing ironstone balls and be- 

 lemnites 64 2 



2. Soft gray sandstone,with a little clay 

 in the composition containing belem- 



nites 23 2 



3. Bituminous shale, fine in the texture, 

 containing belemnites and fossil 

 wood, the bark of xohich is pure coal 26 6 



4. Dark argillaceous schistus, contain, 

 ing many belemnites, marine plants, 

 impressions of large shells and some 



hard ball stones 6 6 



5. Claystone, very fine in the texture, 

 with smooth glossy partings, with a 

 number of small and large petrified 

 shells 18 4 



6. Hard gray sandstone, containing fine 

 streaks of coal with petrified wood 

 in long pieces ; some belemnites and 

 marine shells 15 6 



7. Ash. coloured hard and large-grain- 

 ed sandstone, sulphureous contain, 

 ing large pieces of fossil wood, hard 

 balls, and a few belemnites ; decom- 

 poses when exposed to the air . . 7 10 



8. Very hard unstraii/led limestone, 

 being a mass of shells, wood, bclem. 

 nites, and a few streaks of bright 



coal, all concreted with lime cement 2 7 



Ft. In. 



9. Very hard ferruginous limestone^ 



with calcareous spar in the joints or 

 partings 6 



10. Dark argillaceous schistus, with 

 smooth joints or partings, and some 

 broken marine shells 32 6 



11. Hard argillaceous schistus, the 

 bottom composed of petrified shells 



and a few belemnites 6 



12. An uniform mass of muscle, cockle - 

 and oyster shells, all concreted with 



lime cement 16 



13. Dark argillaceous schistus, with 

 smooth soft partings and a few shells 36 6 



14. Very hard large-grained sandstone, 

 with large shells and wood ; this is 



the roof of the coal 5 



15. Fine cubical coal, with smooth 

 glossy backs, and transverse cutters; 

 burns to a white ash, and has a pecu- 

 liar smell 3 8 



16. Bituminous shale, containing wa- 

 tural oil J burns, but does not con- 

 sume 2 



17. Slate coal with pyrites, not work- 

 able 14 



Bored 15 fathoms in fire clay, alter- 

 nating with argillaceous schistus . 90 



Total ascertained depth . . Feet 338 1 



