174 Account of the Mineral-Fields of Airdrie and Bathgate. 
5th, The mineral-field from the Bathgate Hills to Edin- 
burgh and Leith. 
At Airdrie, and all around, there are very many extensive 
collieries established, not only for the general sale of coals, 
but for supplying the blast-furnaces, for the production of 
cast-iron in the vicinity, which are no less than sixty in 
number. 
The coals of the Airdrie district are the same as in what is 
termed the “ Glasgow coal-field,” with certain changes in the 
arrangement; in particular, where the intermediate strata 
betwixt two coals in the Glasgow district have disappeared, 
and the two coals being brought into juxtaposition, form one 
very thick bed of coal. 
The common clay or argillaceous ironstone abounds here, 
and the Mushet ironstone band, discovered by Mr David 
Mushet, who established the Calder Iron-Works, is very 
abundant, and is of more than double the value of the com- 
mon argillaceous ironstone. It has a portion of carbonace- 
ous matter combined with it, which greatly aids its calcina- 
tion, as very few coals are required for that purpose. 
East from the town of Airdrie, the Glasgow coal-field 
continues, until it reaches the estate of Auchingrey, which 
once belonged to the late Rev. Mr Haldane, where, imme- 
diately by the south side of the turnpike road leading from 
Glasgow to Edinburgh, appears a very great extent of 
“trap rocks,’ commonly named Greenstone, or the “ Blue 
Whinstone”’ of Scotland. These rocks are not much elevated, 
and no doubt they pass under the Auchingrey estate, and 
produce those changes which are commonly connected with 
such rocks. 
These trap rocks are nearly a mile in breadth, and ex- 
tend eastward to the West Craigs Inn. They have evidently 
been forced up through the regular coal-field, and have made 
great derangements ; for the open burning coals of the Airdrie 
district are no longer to be found here, but the anthracite 
(the Blind coal of Scotland), and the caking or smithy coal 
abound ; and there is no doubt that much of the coal in con- 
tact with these rocks is so much changed, that it will not 
ignite, as is always the case in such districts. 
