Coal Mines of Virginia. 129 



or shut, by means of a close door. As the old works are very 

 near the fire, the air in them becomes very much rarified by 

 the heat ; and probably a considerable portion of it is consum- 

 ed (as the principal pabulum for the combustion,) and a par- 

 tial vacuum is produced. When the air in their present works, 

 therefore, becomes impure, they open the door, and a strong 

 current rushes into the old works ; its place is again supplied 

 with fresh air through the shafts. Previous to the adoption 

 of this mode of ventilation, they experienced great inconve- 

 nience from carbonic acid gas ; and some of the workmen had 

 been killed by an explosion of carburetted hydrogen gas. Since 

 this mode has been adopted, they have experienced no incon- 

 venience at all from noxious gases. On inquiry, I was told 

 that the substances passed through, in getting to the coal, va- 

 ried in the different pits. As far, however, as I could learn 

 by inquiry, and an examination of the heaps of rubbish, the 

 following substances, in the order in which they stand, have 

 been found in Heth's pits : — ^mould, clay, gravel, fuller's earth, 

 sandstone, (at first extremely coarse and friable, but becoming 

 more compact and hard, and having an appearance somewhat 

 stratified as they descended,) gray and bluish clay slate, hard 

 bluish sandstone, shale, or, as they term it, shiver, white mica- 

 ceous sandstone, extremely hard ; blue slate and shale inter- 

 mixed, black slate, and then the coal. The depth of these stra- 

 ta differed so much in different pits, that their individual thick- 

 ness could not be ascertained. Vegetable impressions are 

 very common in the slate next the coal ; and they have found 

 the impression of a fish. Pieces of pure charcoal, in the form 

 of sticks, or logs, are frequently found in or on the coal. In 

 sinking one of the pits they met with a perpendicular column, 

 8 inches in diameter, extending through the slate into the coal ; 

 in all about 50 feet. Its surface was distinctly serrated, and 

 at intervals of about 2 inches it appeared jointed, breaking 

 easily at the joints. For the want of a better name I must call 

 it a " lusus naturae ;" for it is neither clay-slate nor mica-slate, 

 nor shale, nor sandstone ; but appears to be composed of them 

 all. Masses of a black oxide of iron are sometimes found in 

 the slate ; and from its weight and hardness the miners verT 



