674 STEVENSON— FORMATION OF COAL BEDS. [November 3, 



rapid decay, the change of that material may advance so slowly that 

 long after the softer parts have been reduced to pulp, the more com- 

 pact materials may remain almost unchanged. The white cedar logs 

 in the New Jersey swamps are so well preserved in many localities 

 as to be serviceable in manufactures, while the thick peat of many 

 swamps in Florida is without commercial value, because it is crowded 

 witli cypress stumps and fallen stems. But decay occurs in the 

 softer woods, so that, as v. Giimbel''^ relates, flattened trunks are 

 found even at a depth of only a meter in loose peat. The flattening 

 was due to rotting, not to pressure. 



The newer peat shows distinct felting and Lesquereux'" states 

 that this condition is marked even when decomposition is far 

 advanced. In peats formed above the original water-plane, the 

 "emerged peats" of tliat author, the layers are characteristic, one 

 inch thick at the top but decreasing downward to less than one eighth 

 of an inch. While the older or ripe peat shows no trace of organic 

 structure to the unaided eye, the microscope proves that it is com- 

 posed of fragments of plants embedded in an amorphous material 

 consisting of humic or ulmic acid, or a mixture of those acids and 

 their salts. He observed that, whenever the growth of the peat was 

 checked by dryness or other causes, 



" tlic upper surface of the peat heconies crusted, Iiarclened and transformed 

 into a thin coating, quite impervious to tlie entrance of any kind of foreign 

 matter : and it is upon this hard upper crust that the boggy humus forms ; 

 or wherever the land becomes resubmerged, a new peat vegetation begins. 

 In which case, such- a crust remains as a parting hiyer l)etween two beds of 

 peat, like tlie well known clay partings between two coal benches." 



V. riiimbel, in the work just cited, asserts that the minute frag- 

 ments of plants are not only intimately mingled and felted but also, 

 in the denser portions, are bomul together and more or less cemented 

 by a luuinis-like substance, which is soluble in a dilute solution of 

 caustic potash. Peat, treated with this reagent and afterwards dried. 



" C. W. V. Giimbel, " Beitriige zur Kenntniss der Texturverhaltnisse der 

 Mineralkohlen," Site. Berich. d. k. bayer. Akad. d. Wisscnschaften. Math- 

 Phys. KL, 1883, p. 126. 



'"' L. Lesqucrenx, 2d Geo). Surv. of Pennsylvania, Ann. Rep. for 1885. 

 p. 118. 



172 



