19".] STEVEXSOX— FORMATIOX OF COAL BEDS. 569 



that great swamps with notable depth of vegetable mud abound on 

 the isthmus of Panama. 



Livingstone, Cameron and others, already cited, have given abun- 

 dant evidence that peaty accumulations are numerous and extensive 

 in the wet regions of interior Africa. Lugard,*''* in describing the 

 region near Albert Edward lake, refers to interminable river swamps 

 and bottomless quagmires, choked with papyrus, which abound in 

 Uganda and Ungoro and cease below about half a degree south from 

 the equator. Miss Kingsley®^ says that she encountered three types 

 of bog in west Africa. The broad deep bog was the least difficult, 

 as it makes a break in the forest, and the sun's heat bakes a crust 

 over it, on which one may go — if he go quickly; the shallow, knee- 

 or waist-deep bog is little more difficult as one can wade through it ; 

 but the deep narrow bog, so shaded that the sun cannot form a crust 

 over it, is the most abundant and the most difficult. " These re- 

 quired great care and took up a great deal of time. Whichever of 

 us happened to be at the head of his party, when we struck one of 

 these, used to go down into the black, batter-like ooze and trv to 

 find a ford, going on into it until the slime was up to the chin." 



Chevalier"" has described an interesting type of peat formation 

 observed in an extended area between the Gulf of Guinea and the 

 sources of the Niger, X. L. 5° to 9°. This great region has many 

 granitic peaks rising to 1,200 or 1,400 meters, but in great part it is 

 a peneplain, 200 to 400 meters above sea level. The southern por- 

 tion is covered with a dense forest but the northern portion is a 

 savannah with only scattered trees and shrubs. The whole region 

 would be naked rock, were it not for the role played by a sedge, 

 Eriosponi /'/Vo.^a Benth., which at times covers the rocks to the exclu- 

 sion of all other forms. It attaches itself to granite and gneiss; the 

 seeds germinate in minute fissures and the roots spread in clusters 

 between thin plates of the rock, altered or decomposed bv atmos- 

 pheric action. When the thin plate of rock has been worn away 



'' F. D. Lugard, Scottish Geog. Mag., Vol. VIII. , 1892, pp. 636-639. 



°° M. W. Kingslc)-, "Travels on the Western Coast of Equatorial Afr'ca," 

 Scott. Geog. Mag., Vol. XII., 1896, pp. 1 19-120. 



™ A. Chevalier, " Les tourbieres de rocher de TAf rique tropicale," C. R., 

 Vol. 149. 1909, pp. 134-136. 



167 



