290 ANNALS NEW YORE ACADEMY OF SCIENCES 



It is evident that conditions necessary for serious destructive work 

 could not exist in the upland area under consideration. In that area, 

 covered by dense vegetation, the waters would collect slowly in the lower 

 portions ; flowing from the humus-covered surface under the forests, they 

 would be almost limpid and with no mineral detritus, carrying only such 

 chance stems as had escaped entanglement while floating through the 

 forest. Even in the broad hollows the flow would be impeded by a dense 

 growth of herbaceous plants, so that rapid movement could be attained 

 only when the water reached the streams; and there alone could a load 

 of detritus be gathered with which to do cutting. There is no conceiva- 

 ble mode whereby vegetable matter growing densely on the upland could 

 be conveyed to the basin. 



In this connection another matter requires consideration. The Bour- 

 ran coal bed, not less than 90 feet thick at Decazeville, is a practically 

 continuous mass, unbroken by persistent .clay partings, and it extends 

 with decreasing thickness over much of the basin. ISTo matter which 

 theory of formation be accepted, transport or in situ, one must recognize 

 that the accumulation of such a mass would require a great length of 

 time. If one accept the transport theory, a great area is essential as 

 source of supply, and equally a vast period of time. The suggestion that 

 a single flood might provide material for a coal bed, by bringing down 

 vegetable debris which had accumulated during a long period, involves in- 

 surmountable difficulties. The total area tributary to the basin could not 

 have exceeded 350 square miles; the material for the Bourran coal bed 

 would require a cover of humus at least 20 feet thick over the whole area, 

 and this would have to be removed by a flood of a t}T)e unknown and 

 operating as no flood of modern times acts, for the whole mass from the 

 whole area would have to be brought down. The suggestion, moreover, 

 is not consistent with an argument offered by its author in support of the 

 delta theory, for it demands a thickness of humus which would be fatal 

 to growing plants. In any event, one can readily see that the inpouring 

 of a flood so terrific in extent would churn up the little lake and all light 

 materials would be driven at once to the outlet, to be deposited far out- 

 side of the basin. 



It is equally difficult to understand how the great bed could be formed 

 by gradual deposit of transported vegetable matter during the vast period 

 of time. One is told that during formation of the sterile deposits, the 

 streams concentrated their attention upon inorganic materials and that 

 during the great floods, they concentrated their attention upon vegetable 

 matter. Such intelligent discrimination on the part of running water 

 is incredible. 



