395 
crop working, usually fanning out from the drift entrance, and if a lot 
of spoil was removed, sometimes having a dendritic form (Fig. 3). 
A similar shape of spoil heap is found where "patchworking", a 
shallow form of opencast mine, was practised in the extraction of coal 
and ironstone. These areas of dereliction are much more extensive than 
those associated with drifts. 
Although greatly reduced in number, levels are still worked today hut 
they are generally referred to as private mines (see Marnell and 
Humphreys, 1965)» They are on a very small scale with work forces of 
only a few men hut the extent of the underground workings is larger than 
in earlier drifts since ventilation and drainage is more efficient. The 
exterior of the mine (Fig, 4 ) rarely exceeds one hectare in area while 
the coal loading plant and buildings housing winding engines (if any are 
used) usually occupy only one per cent of that area. The rest is taken 
up with the spoil heap and storage of pit props and trams. The presence 
of these last two items is an important indication of the activity of the 
mine when seen on the aerial photograph. 
The most significant form of mining, in terms of the spoilation which 
has occurred, has been deep mining where coal has been won at great depths 
by use of vertical shafts and horizontal galleries. The distinguishing 
features of a mine are relatively easy to see on the aerial photograph 
and include the spoil heap(s), slurry lagoons, pithead gear and washing 
and preparation plant. The presence of these features plus stockpiles 
of coal, storage yards containing pit wood and props, railway track and 
wagons, and parked cars are an indication of the mine being active 
(Fig, 5 ). The lack of them does not necessarily suggest a derelict mine, 
however, since sane pit heads are maintained for training, or for 
emergency access or pumping. There is also the point that disused mines 
vary in their state of dereliction, and although perhaps appearing intact 
a mine may be closed. 
Figure 6 shows a mine (Mountain Colliery) which is virtually intact 
although it has been derelict for many years. Apart from a lack of 
railway track and the obvious disrepair of the roofs of buildings there is 
little indication of it being derelict from the air. This illustrates the 
basic problem of air-photo interpretation in work of this nature: not in 
identifying the type of spoiled landscape but in deciding whether it is 
active or derelict. 
The problem is less common with regard to the remaining form of mining, 
that of opencast extraction, since almost by definition, opencast mines 
cannot usually become derelict. After the coal has been removed from the 
opencast pit the overburden is replaced and landscaped before soil and 
grass seed is put down. There are only a few examples in Glamorgan where 
this has not been carried out since for various reasons (at one site the 
contractor had become bankrupt) the opencast working was uncompleted. 
In any case, however, both active and derelict sites are readily 
identified. Both take the form of large excavations in the ground within 
which several levels of working may often be distinguished. Close to the