198 
THE FOSSIL FLORA. 
sive terms,) they contain no foreign admixture whatever. Occasion¬ 
ally thin layers of sandstone, or shale, occur, by which the seam is 
partially divided into two or more parts, indicating a slight partial 
effusion of stony matter over the surface of the vegetable mass, 
whilst it was yet forming; but this is the exception to the rule ; and 
only one instance, that we are aware of, has ever occurred, of a rolled 
fragment of stone being found in the coal, and that was a pebble of 
water worn grey quartz, in Backworth colliery, near Newcastle; we 
may be tolerably certain that such a circumstance is not common, as 
the high character of the .Newcastle coal arises, in part, from the 
total absence of foreign matter. 
Other arguments, to prove that the plants which formed coal were 
either not drifted at all, or at least not from any great distance, may 
he found not only in the perfect state of the leaves of many Ferns, 
but in the sharp angles of the stems of plants which there is every 
reason to believe must have been of a very succulent nature, such for 
example as Favularia tessellata, tt. 73, 74, and 75 of this work; and 
many of the Sigillarias, some of which occur with their surface 
marked with lines and streaks so delicate, that a day’s drifting would 
have injured them. Again, at t. 76, we have figured a cluster of the 
fruits called Cardiocarpon acutum ; had these been drifted one would 
think they must have been dispersed, instead of being collected into 
one spot, just as if they had fallen there from the plant that bore 
them. 
That the fossils which we find irregularly interspersed in the sand¬ 
stones, or shales, of this formation, may have, in some instances, 
originated from drifted vegetables, there is, perhaps reason to believe; 
thus it may have been with Dicotyledonous trees, fragments only of 
whose stems have been traced 70 feet long, without either extremity 
being seen ; these we are sure must have grown upon a dry surface, 
and that surface have been unchanged for many years. And, in 
fact, they are found in just the state in which we should expect to 
find drifted stems, their limbs shattered, their bark beaten and rotted 
off, and their wood in a high state of decay. But that any consider¬ 
able part of the plants which formed the beds of coal were drifted at 
all, appears, from the foregoing remarks, to he highly improbable; 
that they should have been brought by equatorial currents from the 
regions of the tropics, is perfectly chimerical. 
When such a mass of vegetable matter as is now periodically 
brought down by the Mississippi, is deposited upon mud, or sand, 
of which the bottom of some of its branches, or bays, may consist, 
and is there covered by another bed of sand, or mud; is it likely, 
