196 
ANNALS NEW YORK ACADEMY OF SCIENCES 
Renevier recognized that a strong argument in favor of origin from plants 
in situ exists in the conformity of the Grande Couche to its inclosing beds. 
He insisted that if the coal had been formed of in-brought vegetable matter, 
that material, being of low specific gravity, should be found only on the rim 
of the delta cone and in the center of the basin; so that the original declivity 
of the deposit should be very small; but in this area of the Pegauds the coal 
bed shares in the general dip, 25 to 50 degrees, according to the locality. 1 
This observation by Renevier appears to have been regarded as unim¬ 
portant; but it is exceedingly important, for during the Grande Couche time 
the distance from the edge of the plain to the outlet was nowhere more than 
two miles and for the most part not more than one mile, so that during flood 
time the whole surface of the little pond was in rapid movement toward that 
outlet. It was impossible for the velocity of water flowing in from flooded 
streams to be checked so rapidly as to permit precipitation of fine materials, 
the equivalents of impalpable mineral materials, to begin within a few rods. 
The pond was not a deep body of great size, but it was a small body with an 
outlet. The fine clays and the vegetable matter, including the trees, would 
find their way to the outlet; if that were shallow, the velocity would be 
checked there and the coal deposit should be found along the southern 
border of the basin, not on the border of the delta plain. 
The hypothesis that the Grande Couche was once a Corclaites swamp 
demands shallow water in the Pegauds pond; the other hypothesis requires 
that the pond be deep. 
From 500 to 800 meters of stratified rock, much of it very coarse, inter¬ 
venes between the Grande Couche and the northern border of the basin; 
the less coarse materials had been carried farther out. According to Fayol’s 
map, the Colombier had dug for itself a valley comparable to that of the 
Bourrus, yet its delta had been pushed out only one kilometer, when that of 
the Bourrus had almost reached the southern border. The explanation is 
simple. The Bourrus was cutting its way through granites and carrying 
vast quantities of coarse stuff; the Colombier was cutting its way first 
through sedimentary rocks of Lower Carboniferous age and afterward 
through mica schist and gneiss, rocks readily disintegrating and yielding 
comparatively fine material, most of which was not dropped at once but 
was spread over the bottom of the pond. If one consider the character of 
the rocks, he is apt to conclude that the amount of detritus carried out by 
the Colombier was greater than that transported by the Bourrus — and, if 
one may judge by the map, Figure 3, this coincides with Fayol’s opinion. 
The northern portion of the Pegauds pond must have been very shallow 
1 Reunion etc., pp. 67, 68. 
