COAL-FIELD OF CLACKMANNANSHIRE. 145 



in contact with the alluvial cover ; but this coal is 

 altogether an exception to any other coal-field I 

 know of. 



It is proper here to make a remark upon a state- 

 ment generally given in describing the favourable 

 situation of coals found in any extensive district of 

 country, That the coals are found very near the sur- 

 face; whereas it is evident that every coal whatever, 

 excepting when cut off by a slip or dike, is found at 

 the rock-head immediately under the alluvial cover, 

 perhaps at a few feet from the surface, correspond- 

 ing exactly to the depth of the alluvial cover ; at the 

 same time, each coal thus found at the rock-head, 

 is found also at a great depth, according to the 

 angle at which the strata of the coal-field dips. 



Although I have only represented in the section 

 the two great slips or dislocations of the strata which 

 form the three subordinate coal-fields, there are 

 many other dislocations comparatively very small, 

 not only running in a parallel direction with the 

 great slips, but in every various oblique direction. 

 These I have not inserted, as they would only have 

 rendered the section exceedingly intricate, and not 

 easily understood. The section, however, shews the 

 great prominent features connected with the natu- 

 ral phenomena of the coal-field. Fig. 2. Plate IV. 

 represents a horizontal plan of the Clackmannan- 

 shire coal-field, as if the strata at the rock-head 

 were denuded of the alluvial cover. For the sake of 

 perspicuity I have only represented two of the beds 



VOL. III. k 



