114 Vegetation of the First Period of mi AncieiH World. 



little tenacity between the sides of the pot and die stone which fills 

 it up ; this circumstance renders these troubles very dangerous, par- 

 ticularly when they are of a "large size, as they fall without giving 

 any warning. The peculiar singularity attending this trouble is the 

 twisted texture and alteration which are found in the bed of coal im- 

 mediately under and adjoining it, without any mixture of the stone 

 iji it which fills up the pot. There is sometimes no lining of coal, 

 and it generally happens that a piece of the stone which fills up the 

 pot adheres to the upper part of the cavity, so that the trouble may 

 go farther up into the strata than is imagined. This trouble rec|_uires 

 to be minutely investigated, and tire pavement upon w^hich tlie coal 

 rests should be examined under the trouble, to ascertain if it is in 



4 



any way altered in its structure, as is the case with tlie coal. I am 

 indebted to my much respected friend, Mr. Bald, for this latter in- 

 formation. I am happy to say that it is his intention, at an early pe- 

 riod, to devote his attention to these singularly curious objects* 



Were further proof of the vegetable origin of coal wanting, the fact 

 of finding impressions of the seginarise in the solid coal, the thin lay- 

 ers of incoherent carbonaceous matter, having much of the silky as- 

 pect of charcoal, alternating with layers of good bituminous coal, 

 and bearing the form of the calamites most perfect, should go far to 

 establish the vegetable origin of these combustible beds. 



Having now troubled you with the few facts I have been able to 

 collect in the coal districts further south, to which I have added some 

 iremarks on the troubles in the Scotch coal basons, I shall add some 

 short observations on the neighborhood of this city. Here again I 

 have been fortunate in obtaining many specimens of vascular crypto- 

 gamic plants, wdiosc natural substances have been transubstantiated 

 into the sedimentary deposits in which they were entombed, with the 

 exception of their bark or outer coating, which is always much car- 

 bonized. The prevailing plants of diis district, like those of the 

 NewcasUe field, appear to be the segillariee, the scglnaria), the stig- 

 mai'ia?, with a number of calamites. 



I beg leave here to mention, that in die neighborhood of Burntis- 

 land, in Fifeshire, one of these vegetable fossils, the stigmaria of 

 Brongniart, the lepidodendron of Sternberg, with strong impressions 

 of their leaves, occur in a limestone. This is a circumstance by no 

 means of common occurrence. This limestone is devoid of any 

 testaceous or coralline remains, and in appearance, and composition 

 by analysis, varies little from the limestone of the Portland oolite. 



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