274 
trees would maintain that position only as long as they floated, and 
that they would fall and lie prostrate when grounded on shoals or 
cast ashore. He agrees with Mr. Hawkshaw in the opinion, that 
it is more difficult to account for a number of great trunks being de- 
posited in the position of the fossils in the Manchester railway, than 
to imagine that they grew on the surface of the bed on which they 
now stand. ‘Their position on a bed of coal is another proof, Mr. 
Bowman conceives, that the trees were not drifted, for if they had 
been transported by currents of water they might equally have been 
imbedded in the alternating shales or sandstones. If beds of coal 
are the accumulated remains of many generations of a luxuriant ve- 
getation, the rich compost thus formed, Mr. Bowman argues, would 
be well suited for the growth of trees. Again, the angle at which 
the roots of the fossil trees, particularly of that distinguished by him 
as No. 2, dip towards the bed of coal, is considered by the author 
evidence of the trees being in their original position, because, had 
they been drifted, the roots would have been bent upwards, by the 
downward pressure of the trunk, when the water had left them. 
The appearance of the roots being cut off, where in contact with 
the coal, he is of opinion, may be explained by the fermentative 
process having dissolved the vegetable texture below the surface. 
The stems and upper portions of the roots standing above the coal, 
he explains by reference to similar phenomena in peat marshes, in 
which the bases of the trunks of ancient forest trees stand with the 
roots exposed, owing to the shrinking of the surrounding peat. 
3. In discussing the third point, that the trees became hollow 
from the decay of their wood, and were filled with sedimentary 
matter after their immersion, Mr. Bowman refers to the facts re- 
corded in the preceding paper by Mr. Hawkshaw (see ante, p. 269.) ; 
and in confirmation of them states, that Mr. Schomburgk during his 
four years’ travels in Surinam repeatedly observed similar pheno- 
mena. Mr. Bowman then proceeds to explain the processes by which 
he conceives the fossil trees were gradually submerged—their upper 
branches torn off—their interior removed by natural decay,—their 
bark converted into coal,—their central cavities filled with sediment ; 
and the whole buried beneath the stratum of shale or sandstone in 
which the trees were discovered. He afterwards applies the phe- 
nomena which he believes these processes produced to the condition 
and position of the trees and the arrangement of the surrounding 
sedimentary matter. The author then enters into the inquiries, Ist, 
the time which the trees may have required to attain their dimen- 
sions; and consequently the minimum of years requisite for the accu- 
mulation of the vegetable matter; and, 2ndly, what thickness of 
vegetable matter was necessary to form the stratum of coal nine 
inches thick, over which the trees stand. Mr. Schomburgk is of 
opinion that a dicotyledonous tree which would require in temperate 
climates one hundred years to attain a certain diameter, weuld arrive 
at the same dimensions within the tropics in sixty or eighty years. 
The largest of the fossil trees forming the immediate subject of the 
paper is equal in circumference to an oak of 130 years growth in 
