178 Account of the Mineral- Fields of Airdrie and Bathgate. 
thick, is accompanied with a parrot or gas coal, about a 
foot thick, and also with bands and balls of clay ironstone. 
2d, The common argillaceous or clay ironstone, yielding 
from thirty to thirty-three per cent. of iron. 
3d, The curly band ironstone, which is very irregular in 
its form, is of the best quality for producing grey cast-iron, 
strong in its texture, and suitable for artillery. It was 
lately analysed by Dr Thomson junior, of Glasgow University, 
and found to contain no less than forty per cent. of iron,—a 
produce equal, if not superior, to any ironstone in Scotland. 
In future the ironstones found in sinking will be carefully 
registered, as well as those found in broken ground, by the 
side of brooks and in ditches. 
Light-coloured Argillaceous Rock, termed Fire-Clay. 
This mineral is found in great abundance in the Bathgate 
coal-field, from a few inches to several feet in thickness. It 
is of good quality, fit for all furnace purposes, and for some 
kinds of pottery; it is, however, of no value at present, nor 
can be so until the railway now forming is in operation. 
It is a remarkable fact in natural history that, in general 
the beds of coal rest upon this kind of rock, although at 
times but very thin. 
Sandstone. 
There are several quarries of sandstone in this mineral- 
field, suitable for general purposes, but none for elegant 
architectural buildings, Binney quarry excepted, which is of a 
very superior kind, and presently used in the chief buildings 
of Edinburgh. 
Sandstones have been searched for by boring ; and one bed, 
of a white colour, thirty feet thick, was found; but no quar- 
ries have as yet been opened up in consequence. 
Millstone and Flagstone. 
These varieties of sandstone have been opened up at a 
place named Bogend ; the millstones are of a very dark and 
