PART 4.] 
Theobald . Beds with fossil wood i/i Burmah. 
SI 
(a ).—This bed which we may fairly suppose to have been once co-extensive with the rest 
of the group is now greatly diminished in area by denudation, which its mineral character 
even more perhaps than its position at the top of the same has tended to encourage, so that 
even within the ai’ea where it is at present best preserved it by no means constitutes the 
entire surface, being everywhere deeply scored through to the underlying beds below. The 
surface is everywhere protected by a gravcdly layer composed of small quartz pebbles and 
ferruginous concretions derived from pebbly strings and irregular courses of conglomerate 
dispersed through the sand, which readily washing away leaves the residual layer in 
question at top ; to the protection afforded by which against further waste, the existence 
of what still remains of this incoherent bed is largely due. This surface layer is of 
variable thickness, its development being, to some extent, a measure of the denudation 
this group has undergone. On the surface and impacted in it at different depths where 
it is very thick lie logs of silicified wood of all sizes from a foot or so to trunks of 40 and 
50 feet, not entire, but jointed up into pieces of various lengths through spontaneous fracture, 
probably brought about by their own weight, and irregular subsidence during the removal 
of the friable matrix wherein they were originally encased. Though, as a rule, these large 
logs occur as described in a gravelly debris, they sometimes occur relatively to the incoherent 
sand so as to leave no doubt of its being the bed wherein they were originally deposited, 
and on which they may be sometimes seen apparently in situ, as between Thanat-ua and 
lviungee, and not only in this bed hut in the beds beneath it, the same fossil-wood occurs, 
though in smaller pieces, and much less abundantly. The larger logs are quite unrolled, 
hut the smaller pieces are often rounded by transport, though never to the extent seen 
in the pieces of fossil-wood contained in the recent gravels. When this sand rises into 
hills, the sides are invariably steep, and not unfrequently scarped, exposing a clean vertical 
section of sand with its crust of gravel at top. This sand weathers into curious pinnacles 
wherever an isolated stone, shell, stick, leaf, or other foreign body has afforded shelter 
from the direct impact of rain, and the incoherent rock all round washing away eventually 
leaves the protecting substance perched on a. slender pinnacle of sand, which recalls the 
similar phenomenon of the “ earth-pillars of Botten” figured by Sir 0. Lyell in the 10th 
Edition of his “ Principles.” 
In color this sand is greyish, very fine and uniform, and with only a certain admix¬ 
ture of impalpable argillaceous matter forming, where exposed, to traffic, a fine dust, or, 
in the beds of streams where the argillaceous portion has been removed by water, a clean 
silver sand very fatiguing to travel over. Though the sand I am describing unquestion¬ 
ably contains silicified wood, yet it seems probable from the great abundance of large 
trees strewed over the surface, that they existed more plentifully in that topmost portion 
which has almost disappeared through denudation leaving only these bulky memorials behind 
it, than elsewhere. The structure of the wood has been to a considerable extent obliterated 
by decay before its mineralization was effected, and aU that can he definitely said of it is 
that the wood is exogenous and not a conifer. I have remarked but one species in Pi-onie, 
though the Burmese, from trivial distinctions in color and weathering, affect to recognise the 
modern Eujin (Hopea suaraj and the Tliiya (Shorea obtusa), an identification of course quite 
illusory. This wood nowhere exhibits any traces of marine action as might have been 
anticipated had it floated about till water-logged in a brackish or purely salt estuary, and 
hence it may he inferred with considerable probability that it floated about in a fresh¬ 
water sea, or chain of lakes fed by a sluggish stream, till it sank where it became 
ultimately silicified. It must at the same time be remembered that the wood found in beds 
containing marine fossils is also free from perforations, but these are small pieces, much 
rolled prior to their entombment and probably under conditions on some sub-marine bank 
unfavorable to the presence of either J J /tolas or Teredo. In some pieces of fossil wood 
I have noticed minute tubular cavities (perforations?) about '02 or less in diameter, which 
might have been produced by some insect whilst the trunk was still standing, but such 
cases are rare. Associated with this sand, and forming sometimes irregular beds in it, or more 
frequently lenticular courses, now thickening, now thinning out, occur some hard sandstones, 
sometimes very fine grained, at others a pebbly grit, or even coarse conglomerate. No regular 
position in the sand can he assigned to these subordinate layers, hut the fine hard sandstone 
often occupies a'high position in the deposit, whilst a coarse conglomerate is not unfrequently 
met with towards its base. Both sandstone and conglomerate are usually richly charged 
with shark’s teeth of small size CLamnaJ, the conglomerate being usually ossiferous as 
