‘ ; 
496 GEOTECTONIC (STRUCTURAL) GEOLOGY. [Book IV. 
tremely shallow water conditions with continuous or intermittent 
subsidence. Unless soon submerged, dead trees would be subject to 
speedy decomposition. It occasionally happens that an erect trunk 
has kept its position even during the accumulation of a series of strata 











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Fic. 214.—E..ect Trunks or SicinuaArRtA IN Sanpstoxr, Cwm Lurcu, HEAD OF 
SwANseA VALLEY, GLAMORGANSHIRE. (DRAWN BY THE LATE Sir W. E. Looan.) 
These stems (the largest 53 feet in circumference) formed part of a series in the 
same rock, their roots being imbedded in a seam of shale (an old soil) full of 
fern-leaves, &e. The specimens were removed to the Museum of the Royal 
Institution of South Wales at Swansea. 
around it (Fig. 215). We can hardly believe that in such cases any 
considerable number of years could have elapsed between the death 
of the tree and its final entombment. From the decayed condition 
of the interior of some imbedded trees, we may likewise infer that 
accumulation of sediment is not always an extremely slow process. 
Instances occur where, as in Fig. 216, while sand and mud have been 
accumulating round the submerged stem its interior has been rotting, 
so that eventually a mere hollow cylinder has been left, into which 
sediment and different plants (sometimes with the bodies of land 
animals) were introduced from above.* Large coniferous trunks 
(as in the neighbourhood of Edinburgh) have been imbedded in 
sandstone, and have had their internal microscopic structure well 
reserved. In such examples the drifted trees seem to have sunk 
with their heavier or root-end touching the bottom, and their upper 
end pointing upward in the direction of the current, like the snags 
1 De la Beche, op. cit. p. 501. 
* The hollow tree-truanks of the Nova Scotian coal-fields have yielded a most 
interesting series of terrestrial organisms—land-snails and reptiles, 
