34 



other strata towards the south-east at an augle of 25°, and situated 

 higher than the limestone. 



At the south-west termination of this space is situated the Quarry 

 of Burdiehouse. It is difficult to determine, from the covered state 

 of the ground, whether the bed of limestone here seen is lower or 

 higher than the mountain limestone hitherto described ; possibly the 

 mountain limestone may here thin off, and be replaced by the Burdie- 

 house bed. The appearance of the strata, however, which crop out 

 between Burdiehouse and Loanhead, dipping near the former site 

 towards the south-east at an angle of 30°, and towards the latter at 

 a less angle in the same direction, shew that the limestone of 

 Burdiehouse, in common with the mountain limestone cropping out 

 between Edmonstone and Muirhouse, is lower, and therefore of older 

 formation, than the coal-measures of Gilmerton and Loanhead. Hence 

 the limestone of Burdiehouse and the mountain limestone of marine 

 origin, are jointly referable to one common epoch of formation. 



The Burdiehouse limestone, however, is clearly not of marine, but 

 of fresh-water origin. It forms a bed of twenty-seven feet in thick- 

 ness, composed of strata about four and a-half feet thick, dipping 

 south-east at angles of 23° and 25°, with the seams of stratification 

 regular and continuous, and also with intersecting vertical seams. 

 The bed is sui-mounted by bituminous shale, with which very thin 

 layers of limestone occasionally alternate. The colour of the lime- 

 stone is grey, brown, and occasionally purple ; its fracture conchoi- 

 dal, but often slaty, from the intervention of thin strise of vegetable 

 or bituminous matter ; its texture hard and compact ; its aspect dull, 

 and it is not crystalline like the limestone of neighbouring quarries. 

 It is tolerably pure, shewing little foreign matter except what is bitu- 

 minous ; and this is often disposed between the layers of the lime- 

 stone where its structure is slaty. But its most remarkable charac- 

 ter is the nature of the organic remains contained in it. These are, 

 in the first place, plants belonging to the oldest vegetation of the 

 globe ; among which the Sphenopteris affinis, S])henopteris bifida, 

 Lepidostrohus variabilis of Mr Lindley, and various kinds of the Le- 

 pidodendfon, seem to be ascertained. The species are numerous and 

 distinct, so as to afford the most beautiful specimens that can be con- 

 ceived, and a rich store of observation in fossil botany. But, second- 

 ly, the animal remains are even more interesting. One fragment of 

 a fish, which, when entire, must have measured a foot in length, is 

 closely allied to the fresh-water species of the family of Cypnnidm. 

 Innumerable minute animals referable to the fresh-water Entonio- 

 straca are also to be seen ; one of these is probably a Gypris, and 

 indications have been found of minute Conchifera, and of coprolites 

 in great abundance. 



