172 Dr Hrszert 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 Il.—MINERALOGICAL 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 striz 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- 
