210 SIR ROBERT CHRISTISON, BART., ON FOSSIL TREES 
10 feet of it at most has been removed, and undoubtedly much more of it still 
remains in the floor of the quarry. The segments in the Botanic Garden show 
that they are not flattened, but rudely cylindrical, nearly 9 feet in girth, and 
more fluted on the exterior than any other of the Craigleith fossils. 
No. 7, at first supposed to have been a branch, was not attached to any of 
the previous fossils, but was found some yards from No. 5. When entire it must 
have been very like a branch; but its internal structure, which has been pre- 
served more exactly than in any other fossil, will presently be shown to be such 
as to prove that it is not a branch, but a longitudinal section, possibly of a 
trunk. The smaller end is roundly pointed and rugged, as if much worn by 
attrition. 
I have nothing more to add here to what has been already briefly said of the 
position and form of the fossils of Granton quarry. Two fragments, all which 
now remain, except the inaccessible trunks in the flooded quarry, have been 
presented by Mr Howkins to the Botanic Garden collection. One of them 
shows that the fossil to which it belonged was, like No. 2 from Craigleith, 
considerably flattened. 
SrructurE.—The Craigleith fossils are at first uniformly covered over their 
whole surface with a jet-black coal-like substance, like what is often observed 
on other fossils of the coal-formation. This is so brittle, and therefore so easily 
detached, that much of it has disappeared from Wiruam’s fossil of 1830, pre- 
served in the Botanic Garden, as well as from those which were discovered 
not long afterwards. But in many places patches of it stillremain. In No. 5, 
removed to the British Museum, the coal-like covering existed everywhere. On 
the upper 23 feet first displayed it was for the most part only 1 th of an inch in 
thickness ; in furrows and hollows ;,th. But lower down, at 6 feet from the 
lowest part excavated, it had increased to $ an inch in thickness, and at the 
lowest depth reached to 2$ inches. Its adhesion to the surface beneath it was 
very slight; but it was impressed with striated longitudinal lines by the surface 
of the subjacent structure. It has exactly the conchoidal fracture, glassy lustre, 
and brittleness of caking-coal. Heat acts on the one exactly as on the other, — 
that is, the coally crust froths up, cakes firmly, and gives off abundance of smoke, 
burning at the same time with a large dense white flame, becoming a coke like 
that from Newcastle coal, and leaving a very scanty ash when incinerated. It 
is, in short, a fine variety of highly bituminous coal, containing very little earthy 
matter. It does not present any appearance of structure when examined with 
the naked eye, or with the microscope by reflected light. Its great brittle- 
ness prevents it from being ground so thin as to be examined by transmitted 
light. 
This crust, and the similar covering of numberless small fossil vegetables 

