118 



BIND. ALTERNATIONS WITH IRONSTONE. 



out, the props or supports of the roof will be removed, the whole 

 upper strata will then sink down, and the upper coal may be safely 

 worked. There is scarcely any water in this mine, and what is found 

 there, is a salt brine, containing common salt nearly pure : it issues 

 from the fissures in the coal with a hissing noise, being accompanied 

 with carburetted hydrogen, (fire-damp.) All the beds of coal rest 

 upon what is called bind, which is an argillaceous shale, more or less 

 indurated, sometimes coloured black by bitumen, and sometimes in- 

 termixed with sand resembling sandstone, but generally, on exposure 

 to the atmosphere, decomposing into a clayey soil, hke the blue and 

 black binds. 



It seems extremely probable that these beds, called bind, which 

 lie immediately under the coal, were once the soil on which flourish- 

 ed the different vegetables that form coal. When I examined the 

 mine, in 1811, the vegetable remains appeared to me the same as 

 those found in other coal-fields ; but at that time they did not attract 

 my attention, except one which is a nearly globular mass, composed 

 of a series of cones within each other, and diverging from a common 

 centre. These have been called " cone within cone" by the miners, 

 but their nature is not well understood. Adolphe Brongniart, in 

 his excellent work on vegetable fossils supposes they may be the seed 

 vessels of a gigantic species of lycopodium. 



The recurrence of frequent alternations of seams of ironstone with 

 thin beds of blue bind, each alternation preserving the same thickness, 

 is a circumstance well deserving attention, as it indicates a periodical 

 succession of causes, probably dependent on the seasons. 



There are a few beds called ruhlyy or rumilly, by the miners ; they 

 consist of loose materials and fragments, which indicate that they 

 were deposited during an agitated state of the water. Many of the 

 other beds have evidently been deposited by tranquil water in a lake, 

 which occasionally became dry land. I have dwelt longer on this 

 subject, than is perhaps consistent with an introductory work, but I 

 was desirous to direct the attention of geologists to an enquiry which 

 has hitherto been disregarded. 



The conversion of vegetable matter into true mineral coal has been 

 admirably elucidated by the experiments of Dr. Macculloch on wood 

 in different stales of bituminization, from submerged wood to peat, 

 brown coal, surturbrand, and lastly to jet, in which the traces of or- 

 ganization are nearly destroyed. These substances, which have been 

 subjected to the action of water only, all yield bitumen by gentle dis- 

 tillation ; but they differ from mineral coal, by yielding also a large 

 portion of acetic acid, which marks the remains of undecayed vege- 

 table substances. Common coal was formerly regarded, as a com- 

 bination of charcoal with bitumen ; but, as bitumen is itself a com- 

 bination of carbon with hydrogen. Dr. Macculloch says, it will be 

 more proper to consider coal as a bitumen, varying in its compo- 

 sition from the fattest Newcastle coal to the driest Kilkenny coal, 



