232 proceedings: geological society 



Clinton problems in the Southern Appalachians. E. O. Ulrich. 



On certain constituents and the genesis of coals. Reinhardt Thiessen. 

 Coals are chiefly composed of residue consisting of the most resistant 

 components of plants, of which resins, resin-waxes, waxes and higher fats, 

 or the derivatives of these, are the most important. 



Living plants are chiefly composed of celluloses and proteins. The 

 former comprising by far the larger bulk, constitutes the framework, 

 while the latter is concerned in the vital functions. With these are 

 associated other substances, among which are starch, sugars, fats, and 

 oils which constitute reserve food-stuffs; waxes, resin-waxes, resins, and 

 higher fats which perform mainly protective functions — as in cuticles, 

 spore-exines, pollen-exines, bark, and waxjr coverings; and resins and 

 gums which are waste products. 



These components differ very markedly in their resistance to various 

 agencies. Those substances involved in the life and support of the plant 

 are relatively labile, whereas those which perform some protective func- 

 tion, or are to be looked upon as waste products, are relatively very 

 stable. The various members of these groups, of course, differ much in 

 stablility and the first group as a whole may over-lap upon the second 

 in this respect. The celluloses, for example, which form a complex, 

 represented by a series of substances, like cuto-cellulose, true-cellulose, 

 ligno-cellulose, hemi-cellulose, oxy-cellulose, lignin, xylan, pectine and 

 nucine, differ considerably and stand about in the order given in their 

 resistance to decomposing agencies. Of all the substances the resins, 

 waxes, resin-waxes and higher fats are the most resistant. 



At the death of the plants, governed by various conditions imposed 

 in the deposit, a partial decomposition, maceration, elimination, and 

 chemical reduction begins, brought about chiefly by organisms, mainly 

 fungi at first and bacteria later. The least resistant components are 

 removed first leaving the more resistant behind in a residue called peat. 

 Peat contains a large amount of cellulose, possibly in a changed condi- 

 tion. The process of decomposition, begun in the peats, chiefly bj r bio- 

 chemical means, is taken up and continued by dynamochemical means 

 into and through the later stages and results in the various grades of 

 coal, such as lignites, subbituminous, bituminous, cannel, and anthracite. 



Of these coals, as far as examined microscopically, the lignites show a 

 marked elimination of cellulosic components and a decided concentration 

 of resins cuticles, spore-exines, and pollen-exines as compared with the 

 peats. The subbituminous coals, although of the same or nearly the same 

 age as the lignites, and originally of similar composition and origin, have 

 been subjected to greater dynamochemical agencies and show a far greater 

 reduction of cellulosic components and a greater concentration of resins, 

 cuticles and exines than the lignites, and are composed largely of the lat- 

 ter groups of substances. In the bituminous coals, the concentration 

 of resins, exines, and cuticles or their derivatives, is such that the coals 

 are chiefly composed of these. The cannel coals are almost wholly 

 composed of spore-exines, or the derivatives of the compounds compos- 

 ing them. 



