Theories of Formation of Coal. 1 05 



feet thick, and lower down, in the succeeding 2000 feet, there 

 are eighteen beds of similar bituminous limestone, one of 

 them only half an inch thick, eleven of them under six inches, 

 and the thickest two feet. Neither the shells nor the nature 

 of the fish-scales are described, but that these are freshwater 

 limestones may be inferred from this, that several of them 

 are mixed with Stigmariae and other plants ; thus associated 

 with the twenty-eighth seam of coal is a '' bituminous lime- 

 stone and carbonaceous shale in alternate layers of one to 

 three inches, with plants, shells and fish scales ;" under the 

 thirty-first, '• with Stigmarise, shells and fish-scales ;" along 

 with the thirty-sixth, '* black bituminous limestone with 

 branches and leaves of Stigmarice well-marked, and very 

 minute shells ;" under the forty -fourth, " with Stigmariae 

 branches and leaves, fragments of other plants, and minute 

 shells." Mr Lyell states, that he observed " not far above 

 the uppermost coal-seams with vertical trees, two strata,, per- 

 haps of freshwater or estuary origin, composed of black cal- 

 careo-bituminous shale, chiefly made up of compressed shells, 

 of two species of Modiola, and two kinds of Cgpris.'^ It is 

 possible, therefore, that the " minute shells" of Mr Logan are 

 Cypris. Beneath the lowest seam of coal are intercalated 

 fourteen beds of what is called a " Concretionary limestone,'' 

 and *' Limestone in concretionary nodules," from one to three 

 feet thick, one of them as much as eight feet, and in one in- 

 stance the limestone is said to contain carbonized drift 

 plants. 



i. Several instances are given of stems of plants standing 

 perpendicular to the plane of stratification ; the first is 2160 

 feet from the top of the uppermost bed. 



a. Calamites " as if in situ^ 



/3. Lower down, 570 feet below «, two upright stems of 

 Calamites, two inches in diameter, coated with coal, start 

 from the top of a dark-grey argillaceous shale, and penetrate 

 into a grey shale with sandstone above. The length of the 

 stems is not given. 



y. Forty feet below is a foot of sandstone and then a foot 

 of shale, and '^ in this shale, and running into the sandstone 



