104 Mr Bald on the Fires that take place in Collieries. 



Fires in the mines there have been for long an every-day oc- 

 currence ; and sometimes such is the intensity of the fire in so 

 thick a coal, that near the surface it burns with a white heat, 

 melts the argillaceous schistus into glass, and converts the pure 

 argillaceous earth, or fire-clay, into a substance similar to the 

 hardest porcelain. But what is more remarkable, the common 

 argillaceous ironstone frequently assumes the appearance of re- 

 gular basaltic columns, of about an eighth part of an inch in 

 diameter. This aggregate mass is so hard, that it is found 

 equal to any material for making turnpike roads, and is so applied. 



At Bilston and Dudley, in Staffordshire, these fires at pre- 

 sent exist. At the latter place, I visited a garden of consider- 

 able extent, where I saw, from the influence of the subterraneous 

 fires, the snow melting as it fell upon it ; and not only very early 

 crops of vegetables are raised there, but no less than three crops 

 of them in the year. Of this garden there is an account in 

 the Caledonian Horticultural Society's Transactions, sent by me 

 to my friend Mr Neill, our secretary ; and it is worthy of my 

 particular remark, that although the fire is near the surface of 

 the earth, all the beneficial effects of moderately increased tem- 

 perature are found, and no detriment results to the growth of 

 vegetables. From this circumstance legitimate conclusions may 

 be drawn, as to the existence of central fire in the earth. This 

 theory I have long supported, and I think it can be substantiated 

 by sound and philosophic arguments. 



In the early periods of working this coal, the spontaneous ig- 

 nition very much vexed the miners. They had no proper system 

 then of working so thick a coal, on which account they sunk a 

 great number of pits within a few yards of each other ; they then 

 wrought the coal from the top of the bed to the pavement, like 

 the frustum of a cone, very wide at bottom ; they made no ex- 

 tended works, as they were so liable to take fire, but, abandoning 

 one pit, instantly commenced another ; and over the top of each 

 deserted pit, they built a cone of brick-work, like a bee-hive, to 

 prevent the air having access to the coal. Many of these pits are 

 to be seen near Dudley, in a circumscribed area, very close to 

 each other, not unlike the ant-hills found in forests. 



In the progress of mining, the working of this celebrated coal 

 jias been much improved, and extensive workings are car- 



