172 Dr Hibbert on the Limestone of Burdiehouse 



in detail. I may merely remark, at present, that it is a bed in 

 which some of the earliest vegetable and animal tribes incidental 

 to the carboniferous epoch are entombed. 



SECTION II.— MINER ALOGICAL CHARACTER OF THE LIMESTONE. 



The limestone of Burdiehouse admits of various tints. It of- 

 ten acquires its bluish-grey or blackish-grey colour from the bitu- 

 minous or vegetable matter which is so abundantly diffused 

 through it. Other tints approach to those of a clove-brown, or 

 even of a lavender-purple. In its composition it shews very rare- 

 ly any crystalline texture, such as is observable in the mountain 

 limestone of neighbouring quarries ; but, on the contrary, while it 

 is of a dull earthy aspect, its consistence is very compact. The 

 hardness of this limestone is considerable. In its fracture it some- 

 times breaks into a slaty form, particularly when it is alternated 

 with thin striae of vegetable or bituminous matter, but, when these 

 are absent, it shivers into irregular fragments which have a con- 

 choidal surface. In the quarry the limestone appears in the 

 form of regular inclined strata, severally about four and a half 

 feet in thickness, dipping towards the south-east at angles of 23° 

 to 25°, while its seams of stratification are so regular as to af- 

 ford, during the process of quarrying, a continuous surface of al- 

 most unlimited extent. The joint thickness of the mass, which 

 is intersected by vertical seams, amounts to twenty-seven feet. 



The Burdiehouse limestone seems to be tolerably pure, ad- 

 mitting in its composition few extraneous substances except those 

 which have a vegetable or animal origin ; for which reason, it is 

 wrought for the kiln with much advantage. It is traversed in 

 various places by small veins of calcareous spar. It contains 

 some little siliceous matter, and the sulphuret of iron may be oc- 

 casionally found interposed between its layers. 



But this rock is the most remarkable for the vegetable and 

 animal remains contained by it, which concur in awarding to it, 

 not a marine but a fresh- water origin ; and hence, the great diffe- 



