506 PAL.ffiONTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 



the flora of a whole country. It has its place in the harmony of na- 

 ture, like the fruits and flowers of our gardens, the grass of the prairie, 

 the trees of the forest. It was destined for the condensation, the pre- 

 servation of carbon, for the formation of coal. For truly, when we 

 examine fossil plants that have been preserved in the shales of the 

 coal, or when we analyze the substance of the coal itself, we find that 

 the plants which formed it have the greatest likeness to those of our 

 actual peat-bogs, viz : the ferns, the club-mosses, the horse-tails, the 

 rushes, the reeds, and especially the resinous trees. The most remarka- 

 ble difference is that all these plants, compared with those of our time, 

 were of a monstrous size. They were, indeed, the mastodons, the 

 mammoths, of the vegetable world. 



Every body is now acquainted with Liebig's explanation of the com- 

 bustion and decomposition of wood. When heat is applied to it, it 

 burns with flame, developing carburetted hydrogen. When woody 

 fibre is brought into contact with air, in a moist condition, it is gradual- 

 ly decayed, viz : changed into mould or humus, by the conversion of 

 the oxygen of the air into the same volume of carbonic acid. Its 

 carbon is then not only preserved, but augmented. When the access 

 of air is restrained, decay, or a slow burning of the wood, is in like 

 manner produced, but the process is different. The disengagement of 

 carbonic acid, though continuous, is slight, and the final result is 

 charcoal, wood-coal, lignite, mineral-coal, anthracite, even diamond, 

 according to the conditions under which this slow burning has taken 

 place — the quantity of water, the more or less free access of the oxy- 

 gen of the air, compression, heat, &c. Says Liebig: "A slow but con- 

 tinual removal of oxygen in the form of carbonic acid, from layers of 

 wood-coal, or of wood immersed and decomposing in water, transforms 

 necessarily the woody substance into mineral coaL On the contrary, 

 the removal of all the hydrogen of mineral coal, converts it into an- 

 thracite." From this we draw the conclusion, that for the formation 

 of coal, a large production of woody fibre, at a constant water level, is a 

 necessary condition. 



The presence of the water, and its constant level, are necessary not 

 only to prevent a too rapid decomposition of the wood, but also for the 

 vegetation, itself, of the marshes. Plants living entirely immersed in 

 water, do not have a larger proportion of woody fibre in their tissues. 



