COAL-FIELD OF CLACKMANNANSHIRE. 141 



dant in the old alluvial cover, as before mentioned, 

 are part of the strata which are now awanting ; 

 and we have further reason to conclude, that the 

 coals and strata now awanting at the surface, once 

 existed, as we see the lower coals of the middle field 

 again formed, though at a much higher level, im- 

 mediately adjoining and close to the north side of 

 the great north slip, so that these coals and lower 

 strata are in one continued stretch, only separated 

 a foot or two by the width of the slip and vertical 

 dislocation. 



With regard to the absolute shape of the Clack- 

 mannanshire coal-fields, they are similar to the 

 shape or form which I have found to exist in all 

 the coal-fields I have examined in Great Britain, 

 which is, that every bed of coal, with the accom- 

 panying strata, is either bason-shaped, or portions 

 of a bason formed by the dislocations of the strata, 

 and by the mountain rocks on which the coal-fields 

 rest. Where the strata assume the mantle-shape, 

 which is rather an exception to the general form, the 

 coal-field is then termed the Inverted Bason form. 

 The most complete and simplest form of a coal- 

 field, is the entire bason-shape, which we have in 

 some instances, without a dislocation. A beautiful 

 example of this is to be seen at Blairengone, in the 

 county of Perth, immediately adjoining the western 

 boundary of Clackmannanshire, as represented Fig. 3., 

 Plate IV. where the elliptical line marked A C B D, 

 represents the crop or outburst of the lower coal, 



