12 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



beds originated as peat bogs. He believed that coal was formed 

 chiefly from the harder species of reeds, and the vegetable matter 

 had been dissolved in an oily substance. The fluidity of the material 

 is proved by the occurrence of thin streaks in sandstone as well as 

 by carbonaceous shale, which contains enough combustible matter 

 to be utilized as fuel. The opinion that stone coal was at one time 

 brown coal and that, in turn, originally peat deserves no considera- 

 tion ; it is merely the notion of a closet student and Voigt is sur- 

 prised that Beroldingen, who had seen so many localities of stone 

 and brown coal and peat, should offer the suggestion. Stone coal 

 belongs to the oldest formations while brown coal and peat are of 

 the newest ; one might as well suggest that a child begat its mother, 

 and the mother, the grandmother. It is sufficiently clear that Voigt 

 conceived that the vegetable matter was first converted into bitumen 

 and then transferred. His memoir was crowned by the Gottingen 

 academv. The prominence thus given to it as well as the emphatic 

 manner in which its assertions were made did much to repress the 

 readiness shown by contemporaries to accept the Heroldingen hypoth- 

 esis in whole or in part. 



Faujas-St.-Fond^" discussing the source of coals occurring in 

 what he terms granitic regions, says that they were deposited in 

 bays or vast basins excavated by' the sea. Currents transported into 

 these receptacles materials from the granites, which became beds of 

 greater or less thickness. Sometimes the seas brought the plants 

 which, along with animals so abound in them, and these accumulated 

 pele mele with the products of terrestrial vegetation brought down 

 by the rivers. At other times the tides deposited on these beds of 

 combustible materials the quartz sand of the sea bottom; at later 

 periods, wood and plants arrived again, were deposited on the sands 

 or clays ; thus were formed the alternating beds of vegetable mate- 

 rial with combustil)le residues of fish, mollusks and marine plants. 



Al. Brongniart^' described in detail the various types of coal, 

 lignite and ]^eat. He evidently accepts \"oigt's conclusion that there 

 is no bond between coal and lignite, while at the same time he hesi- 



'"B. Faujas-St.-]^\)n(l, " Essai de geologic," Paris, 1803, p. 443. 

 "Alex. Brongniart, " Traite eleniciitairc de mineralogie avec des applica- 

 tions aux arts," Paris, 1807, t. 2, pp. 13, 14, 32. 36. 



12 



