generally from twenty-five to forty fatliom, or more j and the 

 fureft means of difcovering- them is to penetrate into thefe hills 

 with an earth'borer, examining the 0.rata every tvsro or three 

 feet ; if alternate flrata of indurated clay, fand, flate, or fand- 

 ftone occur, with iron ore or mica, we may be certain that coal 

 will be found at a greater depth. The beds neareft to the furface 

 arc generally either earthy, llaty or fulphureous, and commonly 

 thin and fcanty, but under thefe, different beds of greater thickr 

 nefs and of a better fort arc found. Coals have alfo been fome- 

 timcs difcovered by collecting the reddifh or yellowifh muddy 

 water that runs down the fides of hills after heavy rains 5 this 

 water is collected in a pan fuffered to fubfide, and gently eva- 

 porated ; if the fediment appears covered with a black fcum, the 

 hills may be prefumed to contain coal. 



Veins of coal are often mentioned, yet in reality coal is fcarccly 

 ever found in veins, but rather in Ms or in /leaps j though thefe 

 beds, from a derangement caufcd by the occurrence of ftone or 

 matter of a diiFerent kind from that which forms the flrata, arc 

 forrietimes thrown into the form of a horfe-fhoe, with the curva- 

 ture downwards, and thus affume the appearance of a vein. 



When a coal-mine is difcovered, its diredlion, that is, its extent 

 in the fame horizontal line, and its inclination, that is, its fall 

 beneath that line, are next to be traced ; as it fhould always be 

 worked at right angles with its direction, and the fiiaft to drain 

 oiF the water fhould be funk in the loweft part. 



To 



