I9I2] STEVENSON— THE FORMATION OF COAL BEDS. 511 



difficult to understand the bearing of some of the arguments upon 

 others. That from geographical extent is unimportant for the 

 Brush creek limestone has been traced 150 miles and it must have 

 had a notable area in the now eroded region at the east. Nor does 

 it seem essential to deposition of sapropel that the water be calm. 

 Potonie has told of extensive lakes in Germany, formerly navigable 

 but now choked with sapropel. The surface of navigable lakes, 

 great or small, is apt to be churned into waves. No reason can be 

 assigned why the Frische Haff, at the mouth of the Vistula, may 

 not be filled with sapropel, provided conditions remain as now. 

 The presence of fragments of land plants is not of itself final evi- 

 dence of deposit in shallow water or on an offshore area; but the 

 discoveries by A. Agassiz hardly relate themselves to the matter, 

 for he did not report the presence of sapropel material in mud hold- 

 ing fragments of rotten wood, though the region is one as favorable 

 to accumulating such material according to de Dorlodot's conception 

 as one can imagine. The arctic creep must be at its minimum in the 

 Gulf of Mexico. One may hardly refrain from suggesting that de 

 Dorlodot has not conceived the problem fairly. Unquestionably 

 the absence of kaustobiolithic materials from deep sea deposits of 

 this day is as perplexing as interesting and the explanation offered 

 by that author may or may not be correct. But that is not the seri- 

 ous problem, for most of the Coal Measures marine limestones are 

 as free from sapropel as are the present deep-sea limestones, so that 

 conditions then were very much like those of this time. The 

 assumption throughout the discussion is that the marine fauna of 

 the limestone indicates very considerable depth of water, the maxi- 

 mum of immersion. Even this is open to question. True, it is in 

 accord with the prevailing opinion, which, having been unchallenged 

 for a long period, has become, for many, one of the fundamental 

 pillars of geology. Studies by palfeontologists in the Appalachian 

 areas lend no support to the belief that deep water covered the 

 Appalachian basin during the Palseozoic and the stratigrapher hails 

 their conclusions with gratification, as they coincide with his own. 

 These conclusions and the arguments supporting them will be found 

 on a later page. The arguments are applicable equally to conditions 

 in other lands. 



