STEVENSON, COAL BASIN OF DECAZEVILLE, FRANCE 287 



unusually great, and the numerous showers were almost tropical in vio- 

 lence; water swept down the hillsides in sheets and petty rivulets were 

 converted into torrents. Yet one traveling through those gorges on the 

 railroad tould see little trace of destruction — even the plants growing on 

 the walls of cuts were uninjured. 



As the Carboniferous climate is supposed to have been tropical or sub- 

 tropical, reference to conditions observed in the tropics is proper. The 

 writer has had opportunity to examine at close range fully 100 miles of 

 the Venezuelan coast, much of western Trinidad and about 50 miles of 

 the Jamaican coast. The slopes in Venezuela and Trinidad are abrupt, 

 and the strata are often inclined at a high angle. Landslides are not 

 rare, and they always leave a broad scar on the face; but elsewhere the 

 only evidence of heavy rainfall is an occasional gully in yielding rock; 

 the vegetation is practically intact on the steepest slopes. Jamaica illus- 

 trates well the relations of rock, rainfall and vegetation. Near Kingston, 

 the rock is a yielding slate on which vegetation can hardly secure a hold ; 

 the rainfall is but 30 inches per annum, yet the slopes are gashed. East- 

 ward, where the rock is better, one sees an occasional gully and here and 

 there a landslide; but for the most part the vegetation is very dense. 

 Where trees have been burned off, Guinea grass has taken prompt posses- 

 sion of the surface on even the steepest slopes, giving great spaces of 

 bright green which are notable features of the scenery. During Novem- 

 ber of 1909, the rainfall in the mountains of the island was excessive, 

 there having been at one locality a fall of 120 inches in eight days, while 

 there were falls of 20 to 30 inches within 24 hours at many others. 

 Banana plantations, with unprotected soil, were washed down the hills 

 and the plants became projectiles with which the flood destroyed vegeta- 

 tion on the lowland ; but the cocoanut forests remained almost uninjured 

 and the litter of vegetable debris covering the ground under them was not 

 disturbed. Where the surface was protected by vegetation, the damage 

 was confined to gullies dug by fallen trees pushed forward by the water. 

 These gullies widened in soft material and trees tumbled into the torrent 

 were carried down to the lowland, where they were deposited pele mele 

 with mineral detritus over the cultivated area.^^ 



It would seem altogether probable that rainfall on slopes along streams 

 could do little toward forming the coal beds of the Decazeville basin. 

 But on the great rolling upland area, drained by the streams and covered 

 by forest growth, the decaying vegetable matter accumulated during a 



13 I am under obligations to Mr. C. Leslie Mais, C. E., of Kingston, for statistics of 

 rainfall In Jamaica, and also for information respecting localities which I could not 

 visit. 



