Account of the Mineral-Fields of Airdrie and Bathgate. 175 
These great changes, produced by the trap rocks, in the 
condition of the coals, are universal through the coal-fields 
of Scotland, and not only so, but the ironstones are affected ; 
for they are, by natural calcination, brought to yield a higher 
per-centage than in their ordinary state. From this we con- 
clude, there can be no doubt that these rocks are igneous in 
their origin. 
From West Craigs Inn, and farther east, the effects of 
the trap rocks are less observable, but they produce changes 
in the minerals; and on leaving this district, we come to 
the outcrop of the lowest ascertained coal in the western part 
of the Bathgate coal-field. 
The first series of coals consists of four beds of coal, of from 
two to four feet in thickness, inclining to the quality of caking 
or smithy coals, and as such are used. These coals dip to the 
eastward at a moderate rate, until interrupted by a slip or 
dislocation of the strata, which could not be seen. It is 
said to throw down the coals to the east; but of this I have 
great doubts, for we can trace no analogy whatever betwixt 
those coals on the west side of the dislocation, and those on 
the east side of it ; but the conclusions drawn regarding this 
dislocation will be particularly noticed, after describing the 
coals from it to Bathgate. 
The coals, from the east side of the dislocation dip east- 
ward to the town of Bathgate, at a moderate rate. These 
consist of seven beds of coal, of from one foot four inches 
to four feet thick, but the third and fourth coals from the 
surface can only be wrought as one coal, along with the 
intervening stratum. Besides these coals there are several 
very thin coals, termed “ unworkable.” 
This term “ unworkable,” requires to be clearly explained, 
as it is much used in describing coal-fields. No coal, how- 
ever thin, is, physically, unworkable; for by cutting away 
either the roof or the pavement upon which the coal rests, 
room can be made for the miner to work the coal; but thin 
coals, and even coals of one foot three inches thick, may be 
workable in a district where coals are scarce, and sell ata 
high price ; when in another district, where there is abundance 
