787 
largest trunks occur in the greatest abundance on or near dark- 
coloured knolls, particularly towards the south-east portion of the 
area, where they lay like broken stems of a fallen forest, crossing each 
other at various angles ; but the majority of the larger trees are di- 
rected towards the north-west. Two of the greatest, measured by the 
author, were 48 and 61 feet in length, and 24 and 3 feet in diameter ; 
but the lesser fragments are generally from 1 to 3 feet long, and 
4 to 12 inches in diameter. Among the fractured trunks which lay 
broken transversely on the sand-hills, Mr. Newbold noticed many 
with the edges sharp, and in nice adaptation, though the fragments 
were several feet apart. 
A few specimens are imbedded horizontally in the sand and asso- 
ciated conglomerate, and a still fewer occur in a vertical position 
rising from 12 to 20 inches above the surface. Mr. Newbold cleared 
the sand from one of these stumps, and ascertained that its lower 
part was imbedded in the subjacent conglomerate; but it exhibited 
no traces of roots. 
The trunks, which are rarely flattened and never invested with 
coaly matter, are branchless, and in general knotless ; though in some 
specimens Mr. Newbold traced places for the insertion of branches ; 
roots also are wanting, but among the masses enclosed in the sand 
some were found, which bore strong resemblance to the bulbous base 
of palms, and others which assimilated to the tortuous roots of exo- 
genous trees. Internally the trunks exhibit a concentric structure, 
though externally they resemble the present palms of Egypt. Some 
specimens examined by Mr. R. Brown were decided to be dicotyle- 
donous, and not coniferous; but one brought from the Nubian. 
desert by the Rey. Vere Monro is stated to exhibit that structure. 
Indications of a jointed appearance are mentioned, but Mr. Newbold 
is of opinion that this calamite or reed-like structure may be due to 
contraction during the process of silicification. Instances of decay 
at the time the trunks were imbedded the author also noticed, the 
interior being partly filled with grit and conglomerate ; ‘and he men- 
tions cases in which all ligneous structure had disappeared. The 
silicified wood varies in character from a white opake crust, which 
crumbles when handled, to agate and flint, and in colour from white 
to grey, brown and red. No decided seed-vessels or traces of leaves 
have been found. 
The author then describes the structure of Gebel Ahmar, situated 
on the northern limit of the “ Fossil Forest,” and of the intervening 
valley. Gebel Ahmar is an irregular ridge, a mile in length and 
half a mile in breadth, rising to the height of about 150 feet above 
the general level of the desert, and it is composed of conglomerate, 
grit and sandstone, the prevailing colour of the strata being red 
(Gebel Ahmar, Red Mountain). 
The stone has been so extensively quarried, and the mounds of 
rubbish are so numerous, that the original outline of the ridge has 
been obliterated; and its present rugged, conical aspect is due to 
those causes, and not to a supposed volcanic origin. The sandstone 
reposes, as elsewhere, on the marine limestone, passing near the 
Oly III. PART Ile 36 
