About using mine plans
Users should note that maps and plans are prepared for a particular purpose and only represent a snapshot at a point in time. For instance, topographical maps such as those produced by the Ordnance Survey are intended to show surface features such as buildings, roads, field boundaries etc. as they stand at the time the survey was made and in as much, or little, detail as the scale of the map will allow. Such maps often resort to the use of symbols to identify named features where it is not possible to accurately represent the feature by other means.
Users should also be aware that prior to 1840 their was no requirement for mining plans to be prepared and it was not until 1850 that The Inspection of Coal Mines Act 1850 required a coal mine owner to keep a plan at each mine.
In 1872 The Coal Mines Regulation Act and Metalliferous Mines Regulation Act made the deposition of plans of abandoned mines with the Secretary of State a statutory requirement. Non-coal mines were not required to deposit plans if there had been less than 12 men employed below ground and this relaxation was perpetuated in all subsequent legislation until 1993. All that was required to be shown on these plans were the boundaries of the mine workings up to the time of abandonment. There was no requirement for orientation with the surface, depth of workings or section extracted information to be shown.
It is unfortunate that many thousands of workings had been abandoned by the time this legislation was introduced and the knowledge and understanding of those unrecorded workings was, in many cases, lost forever. It is also worth noting that the earlier mine plans would have been produced using simple surveying equipment which did not give the accuracy expected in mine plans of today.
Based on the above it can be seen that many records relating to mining, particularly that which occurred prior to 1872, are likely to be incomplete and unreliable and users should always seek professional advice from a suitably qualified mining surveyor or engineer before relying on the information contained within the records.