72 Extracts relating to Coal, <$*c. 



rising: to a great height, and very steep on the skies, is 

 comrhonly composed of strata much harder and of different 

 kinds from those described wherein Coal is found to lie, 

 and therefore unfavourable to the production of Coal; 

 and these mountainous situations are also more subject to 

 dikes and troubles tlwn the lower grounds; so that if the solid 

 strata composing them gave even favourable symptoms of Coal, 

 yet the last circumstance would render the quality bad, and 

 tne quantity precarious. And, on the whole, it may be 

 observed, that mountainous situations are found more favoura- 

 ble to the production of metals than of Coal It is likewise 

 generally found that those districts abounding with valleys, 

 moderately rising hills, and interspersed with plains, some- 

 times of considerable extent, do more commonly contain Coal, 

 and those kinds of strata favourable to its production, than 

 either the mountainous or champaign countries; and a country 

 so situated as this last described, especially if at some con- 

 siderable distance from the mountains, ought to be the first 

 part appointed for particular examination. Plains, or level 

 grounds of great extent, generally situated by the sides of 

 rivers, or betwixt such moderate rising grounds as last de- 

 scribed, are also very favourable to the production of Coal, if 

 the solid strata, and other circumstances in the higher grounds 

 adjoining, be conformable ; for it will scarcely be found, in 

 such a situation, that the strata are favourable in the rising 

 grounds, on both sides of the plain, and not so in the space 

 betwixt them. Though plains be so favourable, in such cir- 

 cumstances, to the production of Coal, yet it is often more 

 difficult to be discovered in such a situation, than in that 

 before described ; because the clay, soil, and other lax matter, 

 brought off the higher grounds by rains and other accidents, 

 have generally covered the surfaces of such plains to a con- 

 siderable depth, which prevents the exploration of the solid 

 strata there, unless they be exposed to view by digging, 

 quarrying, or some such operation. 



Modes of examining . a formation in ivhich Coal is supposed 

 to exist. — The first step to be taken is to examine all places 

 where the solid strata are exposed to view (which are called 

 the crops of the strata), as in precipices, hollows, &c. tracing 

 them as accurately and gradually as the circumstances will 

 allow, from the uppermost stratum or the highest part of the 

 ground to the very undermost : and if they appear to be of the 

 kinds before described, it will be proper to note in a memoran- 

 dum book their different thicknesses; the order in which they 

 lie upon each other; the point of the horizon to which they 

 dip or incline, the quantity of that inclination, and whether 

 they lie in a regular state. This should be done in every part 

 of the ground where they can be seen, observing at the same 



