240 Dr Hiszerr on the Limestone of Burdichouse 
into account, that this increased dip might have been caused by 
some renewed, yet very slow elevation of the Hawthornden sys- 
tem of strata, by which a sort of lateral pressure had been in- 
duced among the contiguous strata of the Burdiehouse system, 
sufficient to increase their inclination from 23° to 56° or more. 
Having at length briefly described the systems of strata to be 
found in the great coal-field of Mid-Lothian, as indicated by 
fractured areas, I shall now confine my attention to the connected 
ones of Gracemount and Burdiehouse. 
SECTION III._THE GRACEMOUNT SYSTEM OF STRATA. 
Before describing the beds to which the limestone of Burdie- 
house belongs, it will be necessary to previously notice the strata 
lying to the west of, and separated from, the Burdiehouse system 
by a line of fissure. The Gracemount system occupies a place 
intermediate to this fault and the trap of the Pentlands. 
A sandstone, which perhaps holds the lowest place in the car- 
boniferous system of the great Lowland valley of Scotland, is com- 
posed of fine, yet very uncrystalline, grains of siliceous matter ; it 
contains little mica; it is of a deep red colour, owing to the iron 
which is diffused through it ; and it is of a soft consistence. This, 
the most deep-seated bed, rises to day in a few places only, and, 
if it is to be traced in the group of strata to the west of the lime- 
stone of Burdiehouse, we must perhaps look for it among the 
upheavings which occur in the immediate vicinity of the range of 
trap rocks, extending from the chain of the Pentlands, with some 
little interruption, to Arthur’s Seat. Most probably this sand- 
stone may be proved to be wholly, or in part, of marine origin, 
—a suspicion which I have formed upon certain organic remains 
apparently referable to this deposit. 
But quitting the consideration of a sandstone, the existence 
of which in the Gracemount system is at best dubious, owing 
to the rocks being here much concealed, I shall proceed with a de- 
scription of what is actually known. 
