192 
ANNALS NEW YORK ACADEMY OF SCIENCES 
tion cones such as are seen at the mouths of torrential streams entering the 
valley of the Rhone or that of the Adige, where one sees a mass of fragments 
from sand to great blocks. But that comparison does not suffice, for much 
of the Commentry plain had been deposited in water and little of the finer 
stuff was dropped at the shore. One must picture to himself a narrow, 
irregularly hummocky surface, covered by coarse gravels and blocks of 
rock, exposed to danger of devastation by rapid floods. 
The rocks surrounding the basin are all “primitive,” — granites at 
the north, west and south, except a very narrow strip of mica schist at the 
north, while gneiss and mica schist are at the east and southeast. The 
basin owed its origin to orogenic movements, and filling began as soon as 
the topography was defined. It was a region of “abundant but not ex¬ 
traordinary” 1 rain; the surface was irregular, the rocks refractory and the 
streams were torrential. Everything was unfavorable to rapid formation 
of a soil cover, but everything was favorable to rapid removal of loose 
materials. The streams, being torrential, were occupied in corrading their 
beds and the valleys were necessarily narrow with abrupt walls. Here and 
there along the course, little parks were formed above obstructions offered 
by more resistant layers or by rock falls from the sides; but with removal 
of the obstruction or with opening of a passage through it, the stream quickly 
cut down its way and freed the surface of the park from danger of overflow. 
The conditions were not those of broad Alpine valleys, remodeled by glacial 
action, but such as one finds in the valley of the Viege descending from Zer¬ 
matt with its close tributary canyons; in the Royal Gorge of the Arkansas 
and the valley of the upper Eagle in Colorado; or in the area surrounding 
the Yosemite. 
The dense vegetation imagined by Fayol would be impossible in the 
drainage area of Lake Commentry. It demands a growth of trees as dense 
as that of a forest in the temperate zone with an undergrowth like that of a 
tropical jungle. A region, such as that surrounding Commentry and les 
Pegauds could have only a sparse growth of trees and the undergrowth 
would be insignificant. 
The estimate is of the whole amount of woody matter produced con¬ 
tinually on the drainage area and this supposed possible product is shown 
to be far in excess of the quantity required to make the coal. But granting 
the possibility of a growth so dense, the query at once suggests itself: How 
could the vegetation be continuous and, at the same time, be carried to the 
lake? 
If the plants grew in the beds of streams or in clefts within reach of 
1 Fayol : Commentry, p. 330. 
