THE CAEBONIFEKOUS SYSTEM. 125 



The peculiarities of the cannel coals, which have been already referred 

 to, have also been ascribed to the vegetation from which they were de- 

 rived; but I think it can be plainly shown that they owe their charac- 

 teristic features to the method in which they have been formed. As the 

 result of many years' study of our coal strata, I suggested, in a paper 

 published in the American Journal of Science in 1857, that cannel coals 

 were formed in lagoons of open water in the coal marshes, and that in 

 these lagoons the completely macerated vegetable tissue — probably for 

 the most part parenchyma — accumulated as a fine carbonaceous mud, 

 and all my subsequent observation has tended to confirm this conclu- 

 sion. The evidence upon which it rests is briefly as follows : 



1st. The cannel coals in their intimate structure are more homoge- 

 neous than the cubical coals, and show nothing of the alternations of 

 bright and dull lines to which reference has been made, and which we 

 may consider as proofs of changing surface conditions in the coal marsh. 



2d. Though not laminated in the sense that the cubical coals are, the 

 cannels are more distinctly stratified like other rocks which are deposited 

 from aqueous suspension. 



3d. The channel coals generally contain a greater percentage of vola- 

 tile matter than the cubical coals, and the gas made from them consists 

 more largely of hydrogen, and has higher illuminating power. All of 

 which is a natural result of their deposition in a hydrogenous medium 

 which prevented oxidation. 



4th. Cannel coals, as a class, contain more ash than the cubical coals, 

 ' and they frequently pass into bituminous shale. This occurs where the 

 water from which they were deposited had a more rapid motion and 

 greater transporting power. It then carried and mingled with its car- 

 bonaceous sediment an increasing and ultimately preponderating amount 

 of mineral matter. 



5th. Cannel coal contains, as characteristic fossils, aquatic animals, 

 such as mollusks, fishes, amphibians, and crustaceans. These are some- 

 times so abundant and of such a character as to prove conclusively that 

 they inhabited pools of water in which cannel coal was deposited as a 

 sediment. Where plant remains are found in cannel, they are usually 

 floated fragments which show the effect of long maceration — fern fronds, 

 for example, being usually skeletonized. 



6th. In the lagoons of open water found in our modern peat marshes 

 fine carbonaceous mud accumulates, which, when dried, closely resem- 

 bles in appearance and properties our cannel coal. 



With such evidence before us, it seems that there should be no great 

 difference of opinion as to the origin and mode of formation of cannel 

 coal. 



