110 Lord Greenock on the Coal Formation of the 
These lines are merely noticed here, in order to convey a ge- 
neral idea of the space occupied by the coal districts of the Scot- 
tish Lowlands ; but they can by no means be considered as defin- 
ing their precise limits with any degree of accuracy. On the 
south side of the great valley, these coal-measures follow the si- 
nuosities of the transition hills by which they are bounded in 
that direction. Towards the north, although secondary strata 
referable to the lowest members of the carboniferous series are 
met with, skirting the base of the North Highlands, no workable 
coal (of the same formation) appears to have been found beyond 
the Tay, or to the northward of the boundary Mr Wii1ams has 
indicated. 
Although coal may not occur in equal abundance in every part 
of the district included within the limits specified, the causes by 
which it was produced having probably been influenced during 
their operation in a greater or less degree by local circumstances, in 
consequence of which a more copious deposition of the vegetable 
and bituminous matter from which this valuable combustible was 
derived, as well as a greater or less difference in the organic contents, 
or mineral character, of the associated strata may have taken place 
in some situations than in others ; yet, when we consider that, with 
a few exceptions, only occasioned by the partial intrusion of rocks 
of’another description, the whole extent of this space is occupied 
by an alternation of limestones, sandstones, slate clay, bituminous 
shale, coal, and ironstone, containing all the characteristic indica- 
tions of their being members of the same formation, we have fair 
grounds for supposing, that although now separated into different 
fields or basins, the whole of the coal-measures throughout this 
extensive district were in all probability originally connected: the 
strata appearing to have been deposited more or less in a hori- 
zontal position, according to the force of the currents by which 
their materials had been transported, and to the nature of the sur- 
face upon which they were thrown down at the bottom of the s ea, 
that must then have covered at least the whole of that portion of 
