I91I.] STEVENSON— FORMATION OF COAL BEDS. 603 



observation that evaporation from that moss is proportionately less 

 than from other plants ; and he showed that growth of the moss is 

 checked by freezing and that the plant cannot live in deep shade or 

 under forest trees such as oaks, pines or beeches. He seems to be 

 the first to note that marls covering peat bogs contain impressions 

 of plants. 



Lesquereux's conception of the mode of filling depressions from 

 the sides differs somewhat in detail from that given for the United 

 States. Shallow ponds are invaded by vegetation, which forms a 

 mould in which water plants take root. The basin is filled by their 

 decay, the surface becomes humus in which plants of other types 

 grow, giving meadows or forests. The filling is rapid in the early 

 stages. Pools of quiet water are invaded by confervce, mingled with 

 infusoria, microscopic plants and small shells, which by decay cover 

 the bottom. At times, 6 to lo inches of this deposit may accumu- 

 late in a year. When the water is deep, the same result is reached 

 by another process — the prolonged growth of certain floating mosses, 

 especially of some species of Sphagnmn. Those, pushing out from 

 the sides, form a thin cover, in which grasses, sedges and other 

 water-loving plants grow. Eventually, this becomes compact enough 

 to bear the weight of trees, even of dense forest; until, becoming too 

 heavy, it either breaks or is pressed slowly to the bottom and covered 

 with water. This, he asserts, is no hypothesis but the statement of 

 actual fact. 



The lac d'Etailleres, near Fleurir in Switzerland, is open water 

 in an extensive series of peat bogs. Prior to the year 1500, it was 

 the site of a forest ; but in that year, according to legend, the forest 

 disappeared and it was replaced by two lakes. The lakes still exist 

 and in quiet water one can see the prostrate trees on the bottom. 

 But a new carpet has already spread over much of the surface, which 

 in turn will become forested and will sink. Thus one mav find 

 superimposed beds of decomposing vegetable matter, each consisting 

 of remains of small plants below but of forest remains above. An 

 analogous condition exists in Lake Drummond of the Dismal Swamp, 

 where the bottom consists of a forest cover, once at the top but now 



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