626 STEVENSON— FORMATION OF COAL BEDS. [November 3. 



acids. Alumina and sodium chloride seem to always be present, 

 though the latter is in small proportion. 



8. When mature, peat consists of minute fragments of plants, 

 embedded in an amorphous substance, more or less flocculent, the 

 whole cemented b\- an originally soluble substance, which fills clefts 

 in the peat and at times clefts in the underlying deposit and. in the 

 older peat, penetrates even the cell tissue of plant fragments. 



9. In a very great number of peat deposits, one finds erect stems 

 of trees, rooted in the underlying clay or sand. Within extensive 

 areas, the peat mass is crowded with successive generations of trees, 

 which had grown on the peat, their roots not penetrating to the soil 

 below. In the case of the less durable woods, the interior has dis- 

 appeared and the compressed bark remains ; but the prostrated stems 

 of the more durable or resinous woods have resisted decay and they 

 have retained their form ; yet in Quaternary peat, the flattening is 

 more or less marked in all. Peat is not good soil for all kinds of 

 plants even when dry, but, even when wet, it is the soil on which 

 several types of majestic trees thrive best ; when somewhat less wet, 

 it is the habitat of some other great trees, which flourish, while peat 

 accumulates around their stems. 



10. Peat accumulates within the tropics wherever conditions of 

 topography and humidity are favorable. 



11. The deposits of true peat are autochthonous. 



Buried Forest.s. 



Long ago, erect trees with roots and at times with branches 

 attached, were observed in the Coal Measures. Some geologists 

 were convinced that the existence of these trees was proof that coal 

 beds were formed in situ. The force of this argument seems to be 

 recognized by some of those who favor the doctrine of origin by 

 transport, for, in later years, every reported discovery of trees or 

 forest buried /;; situ has been met with incredulity or worse. The 

 writer does not share in the opinion that the presence of trees buried 

 /// loco natali is of serious import as an argument, directly, either 

 for or against any hypothesis respecting the mode of coal bed for- 

 mation ; but, in this, he apparentl}' differs from so many geologists, 



224 



