54 
ST. EE LENA. 
but in some places it has, in its sluggish course, pushed the rubble 
before it until a great heap has accumulated, when either it has 
broken through the mass and continued its course underneath, or 
poured over it in order to resume its way on the other side. An 
instance of this is to be seen to the south of Ladder Hill signal station, 
where an immense accumulation of rubble has been forced forward 
by the huge stream of lava overlying Pierie’s Eevenge. In some of 
the earliest, as well as the latest of these beds, there exist cylindrical 
holes, which are now quite empty, but close examination removes 
almost any doubt as to their once having been filled by stems of 
trees. It is most improbable that trees grew upon any part of the 
Island at that period when the rubble beds were being formed, and 
whether the stems embedded in them grew on some near adjacent land, 
or were floated from some distant country across the sea and through 
the agency of currents into the crater, cannot now be determined ; 
but the latter theory seems very probable because in the present day 
seeds of plants which grow eastward of the Cape of Good Hope aie 
conveyed and cast up by the sea on to Sandy Bay Beach, the l eiy 
centre of the crater. Had these stems been enveloped in the laia, 
they would have been quickly burnt ; this may have occurred with 
some of them of which no trace now remains, but it seems most 
probable that they would be cast out ot the ciatei with the 
.rubble before the ejection ol lava commenced; and we thus find 
them in these beds. The heated rubble would suffice to burn 
the wood, converting it into carbon, which in conjunction with 
steam and other gases would easily cause its disappearance in the 
form of carbonic acid gas, &c., so that, while the rubble would have 
sufficiently hardened to retain a cast of the external shape of the 
stem, no trace of the tree itself would remain. Possibly, remains of 
the wood maj yet be found in some newlv-opened cast. I have 
only seen those which have been long ago cut through in making 
roads, when perhaps if they contained anything it was never noticed. 
Although no remains of the original wood were to be seen in those 
which I examined, there was no difficulty in tracing, on the side of 
the casts, an imprint of the coarsely imbricated form of the stem, 
showing it to have borne the characteristics of a palm or large 
tree fern. 
A very complete cast of this kind, which measures nine inches 
in diameter and forty-two inches in length, occurs in one of the 
