1913-] STEVENSON— FORMATION OF COAL BEDS. 123 



the direction of the wind. Occasionally, several lines are united 

 into a strip, 5 or 6 feet wide, but the bunches are barely in contact, 

 while spaces of 500 to 2,000 feet intervene between the strips. 

 Within the area, where weed is most abundant, the whole mass, in a 

 width of a mile, would form a strip not more than 65 feet wide, if 

 the bunches merely touched; if the material were compressed, so as 

 to bring the parts of each bunch into contact, the strip would be 

 insignificant, not more than 2,500 cubic yards to the square mile. 

 North and south from this small central area, the quantity of weed 

 is unimportant. 



Ochsenius^^^ in 1890 made some suggestions, which in later publi- 

 cations he developed into what is known as the " barricade theory." 

 This has been given in detail on earlier pages in Part I. One might 

 hesitate to regard this " theory " as offered seriously ; but its author 

 presented it in various forms and discussed it elaborately ; some 

 geologists have considered it worthy of refutation, while others 

 appear to have found in it enough of suggestiveness to give it merit. 

 Ochsenius clearly was not familiar with conditions observed in coal 

 deposits and his information respecting river action was imperfect. 

 He cites the statements of writers concerning various localities, but 

 these refer to matters quite irrelevant. The rafts of the Atchafa- 

 laya and of the Red river have no bearing upon the question of his 

 dams. The extent and character of those rafts were grossly exag- 

 gerated by the early observers, but such as they were, they could not 

 be formed on the rivers imagined by Ochsenius, as they required an 

 enormous drainage area. Of course, barricades could be formed at 

 curves of rivers and they are formed ; but they are not such as the 

 " barricade theory " demands. Such a blockade of timber would 

 soon become a dam without lateral spillway, as he suggests; but if it 

 existed long enough, with low water, to permit the fine " Spulgut " 

 passing over to form a bed of carbonaceous shale in the basin, and 

 long enough afterwards, with continuous high water, to permit 



^^C. Ochsenius, " Ueber das Alter einiger Theile der (siid-amerikani- 

 schen) Anden. III.," Zeitsch. deutsch. geol. Gesell, Vol. XLIL, 1890, pp. 135, 

 136; "Die Bildung von Kohlenflotzen," ibid., Vol. XLIV., 1892, pp. 84-86, 98; 

 "Die Bildung der Kohlenflotze," Verh. des. d. Natiirf. u. Aertze, II., 1896, 

 pp. 224-230. 



