114 PERMIAN ROCKS OVERLYING THE CARBONIFEROUS STRATA. 
origin. What then does the finely levigated shale or clunch, which is the sup- 
port of the coal-seams, indicate, but that in those periods when the bottom of the 
sea was spread over with the detritus of matted and broken plants, washed into it 
by inundations or freshes of former rivers, that the heavier earthy matters which 
accompanied such accumulations (in the same way as in the floating islands or 
snags of the great American rivers), sank to the bottom, whilst the lighter plants 
floated, and formed the upper stratum ? 
The plants thus left upon the muddy slime which had either been drifted with 
them or derived from the destruction of the lands on which they grew, were sub- 
sequently covered by other sediment, sometimes in the form of siliceous sand, at 
other times of argillaceous matter impregnated by calcareous springs, thus account- 
ing to us for the varied nature of the roofs of the coal-seams, which consist of grit, 
sandstone, or limestone, according to the condition of the water which succeeded 
the deposit of each layer of vegetable and earthy matter. We may, however, ex- 
press our belief, that here as elsewhere some of the coal which is found in strata 
alternating with marine deposits, may have resulted from the washing away and 
the entombing at shoit distances from their original site, of the low jungle edges 
of tropical islands ; in other words, by the sinking into the adjacent sea of floating 
masses of matted earth and plants. 
Strata overlying the Carboniferous Rocks . — Before we quit the consideration of 
this productive coal tract, we would invite our successors who may have more 
time at their disposal than we had (for the summer was past when we quitted Lis- 
sitchia-Balka), to examine well the succession of strata between that place and 
Bachmuth. Even in our rapid movements, however, we saw enough to convince 
us that the carboniferous strata of the promontory of Lissitchia-Balka fold over 
and dipping to the west and south, disappear beneath other peculiar limestones, 
whilst these again (PI. I. fig. 3.) descend into the vale of Bachmuth, and pass 
conformably under red marl, limestone, sandstone and gypsum. 
In leaving the coal country of Lissitchia-Balka and in passing to Bachmuth, we 
found the series overlying the Carboniferous promontory near the village of Bie- 
lagorskaya to consist, in ascending order, of — 1. Yellowish sandy magnesian flag- 
like limestone, with flattened siliceous concretions and casts of Aviculse. 2. Yel- 
lowish and brown sandstone, with concretions. 3. Massive gypsum. 4. Limestone 
of much lighter colour than any of the adjacent carboniferous region, in parts 
cavernous and tufaceous, in parts sandy and magnesian, with some green grains 
