Theories of Formation of Coal, 107 



aceous shale or sandstone with Stigmarice, in which six feet of 

 the stem are visible. From the root of the plant proceeds a 

 Stigmaria branch, which at first sight had much the appear- 

 ance of being a root of the Sigillaria, but close inspection 

 shewed that the two, although touching, were distinct. 



/M-. The next is 108 feet lower, where, from a grey argil- 

 laceous shale, " springs an upright Sigillaria, eighteen inches 

 in diameter, penetrating an incumbent sandstone." Fourteen 

 feet of argillaceous shale and sandstone beneath do not con- 

 tain Stigmariae. 



V. The next is 133 feet lower, where, from a thin seam of 

 coal with carbonaceous shale beneath, " rises an upright 

 Sigillaria ; the roots spread on the top of the coal ; the plant 

 is a foot in diameter, and only one foot of the length is 

 visible.'* 



J. The next is 160 feet lower, where, from a red argilla- 

 ceous shale, springs an upright Sigillaria. Two feet of the 

 length is seen, but it is cut clean off at the top and at the 

 bottom by the measures which pass both without disturbance. 

 No SligmaricB occur for many yards below. 



0. The next is 101 feet lower, where, from a grey argilla- 

 ceous shale, six feet thick, without StigmaritB, starts an up- 

 right Sigillaria, four inches in diameter ; it is planted two 

 feet in the shale, and penetrates the sandstone above, being 

 four feet in length altogether. 



ie. The next is 362 feet lower, where, from a red and dark 

 grey variegated shale, twenty-eight feet thick, with small balls 

 of ironstone and Stigmaricd, arise two upright SigillaricB. The 

 roots of these spread out just on the top of the bed, and two 

 feet of the plant are visible. The roots of the other spread 

 out likewise, but they sink deeper into the shale by two feet, 

 and the plant penetrates farther into the superincumbent 

 sandstone. 



g. The next distinct instance is 490 feet lower, where, from 

 a grey argillaceous shale, several upright Catamites from half 

 an inch to four inches in diameter, penetrate an incumbent 

 grey arenaceous and argillaceous shale, containing prostrate 

 carbonized plants. The roots of a Calamite three inches in 

 diameter, spread on the top of the shale underneath ; and 



