i9'iJ STEVEXSOX— FORMATION OF COAL BEDS. 631 



" These stumps evidently represent three or four successive genera- 

 tions, growing at higher levels as the surface of the swamp was 

 raised by deposition." Some of them are large and the wood is so 

 hard that it is difficult to detach a piece with the hatchet. No. 5, 

 in some places, is a river alluvium and at times resembles a sandbar. 

 It frequently contains great quantities of driftwood. 



The cypress stumps in Xo. 7 are well preserved and hard, but 

 the driftwood in Xo. 5 is soft and spongy. When water-soaked and 

 resting on the ground it is visibly flattened by its own weight ; one 

 stroke with the hatchet will sever a trunk, 20 inches or more in 

 diameter. But if this soaked material be exposed to continuous 

 sunshine, it not only loses water but also contracts into hard shining 

 lignite, with conchoidal fracture and exhibiting to the eye scarcely 

 a trace of the original structure. A trunk, 6 or 8 inches in diameter, 

 when thus dried, forms a contorted coal layer not more than half 

 an inch thick. The exposed portion of a trunk may be transformed 

 in this way, while the portion, remaining embedded, retains the orig- 

 inal features. These changes are very like those seen in the lignite 

 at Putznach as described by Bischof ; there is evidently a change 

 from soluble to insoluble in some constituent of the trunk. Hilgard^*® 

 had traced the deposit underlying the Orange sands through a great 

 area in southern Mississippi and the features seem to be the same 

 throughout. It " cannot be better described than as the soil of a 

 cypress swamp, with its muck, fallen trunks, stumps, roots and 

 knees. Of these there are evidently several generations, separated 

 by more clayey layers of muck." 



Eldridge"^ mentions a deposit of Eocene lignite in Alaska con- 

 taining 10 to 15 beds varying in thickness from 6 inches to 6 feet. 

 The ash is from 1.85 to 10.68 per cent. The lignite of these beds 

 resembles a mass of carbonized wood. Stumps, i to 2 feet in diam- 

 eter, are common, standing vertical to the bedding. Their appear- 

 ance as well as the abundance of slivers and other carbonized 



^** E. W. Hilgard, "Report on Geology and Agriculture of the State of 

 Mississippi," Jackson, i860, pp. 152, 153, 155. 



"" G. H. Eldridge, "Reconnaissance in the Sushitna Basin, Alaska," 

 Twentieth Ann. Rep. U. S. Geol. Surv., 1900, Pt. VII., pp. 21-23. 



PROG. AMER. PHIL. SOC. , I.. 202 PP, PRINTED N(JV. 17, I9II. 



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