234 



Efflorescence 

 resemblins a 

 field of corn. 



Lime stone. 



Pyrites. 



Specimens of 

 the scliistus in 

 its several 



states. 



ALUM MINE. 



stead of the roof, the originated surface couM not have fallen 

 oft'; but would have covered the inferior portion, and put an 

 eternal stop to the process. Had the coal work been carried 

 on from the lower to the higher part, the waters would have 

 been left to accumulate, and would have dissolved the efflores- 

 cence as fast as it was formed. Or, had this extensive simple 

 apartment been abandoned as is usual in collieries, at much less 

 periods, the same effect would have followed. And, with all these 

 advantages, ii'the length of time had been less, or the extent of 

 surface more limited, the slow process of efflorescence would 

 have been totally inadequate to the supply of a manufactory. 

 Or lastly, if a greater number than usual of pits had not been 

 left unfilled, no circulation of air equivalent to the efflorescence 

 could have followed. 



In these pits is found a very singular efflorescence of sulphate 

 of magnesia growing in fine splculae, about a foot in length, and 

 covering a space of 40 or 50 yards square, like a crop of corn. 

 It has, been much injured by visitors who have trodden it 

 down and taken parts away. 



Lime-stone is got at the same works. It lies over the s<;his- 

 tus, generally about 3 feet thick, more or less. It is horizon- 

 tally separated into two by a very thin seam of crystallization, 

 in which the miners make their blast, which throws down the 

 lower portion, and leaves the upper as the roof. 



Very beautiful effloresced pyrites, the residue of the coal 

 works!, are found among the decomposed schistus, and are 

 worked with other pyrites for copperas. 



Schistus, No. 1. — Ten inches thick native material, very dense 

 even with conchoidal fracture. 

 2. — First stage of decomposition : Dirty light 

 brown ex4:erially, with efflorescence, and 

 numerous small cracks throughout, shew- 

 ing the slaty texture. 

 3. — Third state: More split and weathered. — 

 Many parts flaked oif. White saline, 

 dusty thin covering of efflorescence, and 

 saline matter in the cracks evidently for- 

 cing the them asunder. The salt tastes 

 rough, acid, and ferruginous. Slight wooly, 

 or silky appearance here and there like 

 the flowers of Benzion. 



Fourth 



