'91 1-] STEVENSON— FORMATION OF COAL BEDS. 563 



even moderately extensive areas is wholly without basis in fact. 

 One must regard it as originating in medieval descriptions of the 

 devastating force of the Xoachic deluge, which became an integral 

 part of religious and romantic literature, so that the conception was 

 accepted as a fundamental truth, needing neither investigation nor 

 proof. 



The Phenomena of Peat Deposits. 



Peat or turf is familiar to those living in the temperate zone. 

 It is an accumulation of vegetable matter undergoing special chem- 

 ical change because protected from atmospheric oxygen by an excess 

 of moisture. If one examine an old peat bog, he finds the surface 

 covered by plants of various kinds growing on more or less decayed 

 material. This, in its uppermost portion, is brown or yellowish 

 brown, but the tint deepens downward until in the ripe peat it is 

 almost black. At the top, one finds the vegetable structure distinct, 

 but downward that becomes more and more obscure until in the 

 mature peat it cannot be recognized by the unaided eye, and there 

 seems to be only a vegetable mud containing, at times, fragments of 

 slightly changed wood. 



Peat-making Plants. — Sphagnum is regarded by many authors as 

 the all-important agent in production of peat ; and this supposed con- 

 dition has been utilized more than once to fortify arguments against 

 the suggestion that coal beds originated from growth in situ. The 

 prevalence of this misconception is strange, for evidence to the con- 

 trary has been presented in many works during the last centurv. 



Darwin^- says that in the Chonos archipelago, S. L. 44° to 46°, 

 every piece of level ground is covered with Astilia pumata and 

 Donatia magcUanica, " which by their joint decay compose a thick 

 bed of elastic peat." In Tierra del Fuego, the former is the chief 

 agent. Fresh leaves appear constantly around the growing stem, 

 while the lower ones decay. Tracing a stem downward into the 

 peat, the old leaves can be seen in all stages of decomposition until 

 the whole has become blended into a confused mass. Every plant 



" C. Darwin, " Journal of Researches,"' New York, 1846, Vol. II., 

 pp. 24-26. 



161 



