Coal Mining Operations at Malmesbury
By Professor J. Buckman, F.L.S., F.G.S., &c.
The little Town of Malmesbury is well-known to the antiquary for the remains of its once glorious abbey, its interesting market-cross, and, if I recollect rightly, a cosy hostel, formed out of the ruins of an old conventual building, beside other mediaeval reliques of great interest. Its inhabitants are a primitive race who derive great satisfaction from charter, and still better, from a large piece of rich land bequeathed to them by King Athelstan. Now, whether the king with his bequest gave assurance that, by digging deep, those into whose hands the said land might fall would realise great treasure, or whether some person in digging a well suddenly came upon a black coaly-looking substance in the stratum of clay, does not appear; but we incline to the latter opinion. However this may be, certain it is, that about a century ago, operations for coal-mining were commenced on Malmesbury Common; the timber of the estate was felled to pay the expenses of a shaft that was sunk and, as report said, coal found. Indeed this latter assertion had been verified over and over again, as young natural philosophers (and they were very young in it) had from time to time collected lumps of carbonaceous matter, black as coal, and which on being brought to the unerring test of experiment – the trial by fire – burnt like like coal; in short, were true “black diamond.”
Still with this evidence the mining had been abandoned after the sinking of a shaft – and some money. This latter article, by the way, was supposed to have been raised again by the wary ones whom rumour asserted to have been bought over not to prosecute the work any farther by the coal-masters of another district, in order to prevent the competition which this new mine from its contemplated riches must inevitably produce. Now as this opinion prevailed, it was not long since deemed advisable to re-investigate the matter, but this time it was determined that such investigation should be intrusted to a geologist, and as such I was requested to undertake the inquiry.
Having therefore gone to this most interesting district to prosecute my mission, I was soon in communication with some intelligent gentlemen who represented the estate, when the evidence connected with the opening of a shaft was laid before me. About two pounds weight of previously-mentioned black substance brought from the shaft, was submitted for inspection. This black matter of course proved to be lignite or carbonized wood, thin deposits of which will be found in most thick clay deposits, and very frequently in this which is the Oxford clay. Such appearances, however, have frequently led to fruitless mining experiments, the usual argument for which is, “here is a good burning coal got a few feet from the surface; it is true it is but a thin seam, but how much thicker will it become the deeper we descend.”
In addition to this evidence a bill of sale of some land in the district, on which was a statement that the mining rights were to be reserved, was put into my hands; but it came out that the property in question was crown-land in which such reservation is always made.
Evidence of this character was perfectly valueless, and as it resolved itself entirely into geological investigation, I shall now describe the geological facts of the case.
On going to the site of the old shaft, I soon found that it had been commenced in the Oxford clay formation, and from examining the exposed debris of the shaft, I became convinced that the opening of nearly one hundred yards in depth as stated by my guide had not pierced through the Oxford clay bed.
Here, then, the question of obtaining coal on this spot was at once set at rest, inasmuch as we should have many thick formations to penetrate before arriving at the usual position of coal-bearing beds. There would be in descending order, as follows:-
- The Oxford clay with its basement of Kelloway rock.
- Forest marble.
- The Great Oolite beds.
- The Fullers’ earth.
- The Inferior Oolite beds.
- The Lias formation.
- New Red Sandstone group.
The aggregate thickness of which would not fall far short of 3,000 yards. Here, then, it became evident that it would be rash in the extreme to recommend any operations in search of coal, as even if it were proved to exist below the formations cited it would be far beyond a mining depth, and besides we are quite without evidence of its quality or value. In this case it will be seen that although geological evidence was not sought until after much money had been expended in what is called a practical way, yet that a first inquiry by geologist would have settled the matter; and that, without the slightest recourse to mining operations and their concomitant heavy expenses.
Webmaster’s Note: The Oxford Clay is said to be thicker than 100yds deep at the common but appears to only be about 5 feet deep at the Dyson site on Tetbury Hill.