148 COAL-FIELD OF CLACKMANNANSHIRE. 



miles distance from the Castlehill, and beyond the 

 crop and outbursts of all the workable coals in the 

 true bason-shaped part of the field ; at the same time, 

 by this inverted bason-form, these beds of limestone 

 are found elevated far above the level of the com- 

 mon surface of the country, and consequently above 

 the level of all the coals. The numerous beds of 

 coal, one of which is of the very great thickness 

 of 30 feet, lie next the Castlehill, in a conforming 

 situation with the beds of limestone, as represented 

 in one side of this section. This hill is of an el- 

 liptical form, and the coals are found all around it. 

 Besides the Castlehill thus described, there are two 

 other hills which, with the Castlehill, lie in a di- 

 rect line through the coal-field : These are named 

 Wrensnest Hill and Hurst Hill. Fig. % Plate VI. 

 represents Wrensnest Hill, with the same beds of 

 limestone as found in the Castlehill, which have 

 also been wrought to a great extent, by means 

 of a canal cut through the hill, which gave me an 

 opportunity of examining the internal form of the 

 strata of the hill, as represented in the figure, 

 which are completely mantle-shaped. This hill is 

 also of an elliptical form, and the beds of coal with 

 their accompanying strata, lie all around it, con- 

 forming with the beds of limestone, cropping to- 

 wards the summit of the hill. From the truncated 

 figure of the top of the hill, which is now arable 

 land, it would appear, that at one time it had been 



