RECENTLY DISCOVERED IN CRAIGLEITH QUARRY. 211 
found in the beds of the coal-formation, have been usually regarded as fossilised 
bark, and Mr Wirnam expressly endorses that opinion. But it will be seen 
afterwards that the coaly crust cannot have been the bark, at least in the case 
of the Craigleith fossils. 
It had evidently covered every part of No. 7, the capione branch,— 
its entire girth, and even the whole of its rugged worn point, although, for 
reasons to be given presently, the greater part of that fossil could never have 
had any bark upon it at all. 
The black crust left here and there on WitTHam’s fossil, No. 2, and on those 
at Rockville Villa and Barnton House, Nos. 3 and 4, has the same appearance 
as that of No. 5, but is less brittle, does not froth up or cake when heated, 
gives off less flame and smoke, and leaves more ash after incineration. It is 
still a very bituminous coal, but is much more earthy. 
The structure of the fossils below this thin crust is totally different. All 
the investigations made on this subject agree exactly with the excellent descrip- 
tion and drawings of Mr WirTHAwm’s papers, and confirm his deductions by some 
facts which did not come under his observation. 
The structure of No. 6, the lowest fossil in the quarry, and that of No. 7, 
the “branch,” are the most distinct and interesting. No. 6 is much more 
brittle than the others; it is of a darker grey colour, and it leaves a fine brown 
dusty stain on the fingers when handled. The longitudinal fracture is in many 
places finely fibrous to the naked eye, and exactly like the fibrous appearance 
of wood; and, not unfrequently, such fractured surfaces present in great 
abundance to the naked eye the transverse parallel lines which denote trans- 
verse medullary rays. Cavities often occur, very ragged on their inner surfaces, 
filled with a fine charcoaly matter, and sometimes lined with crystals of pearl- 
spar and calc-spar. From such a cavity I have a specimen of transparent 
erystals of calc-spar as large as the finger nails. Thin translucent plates of 
the fossil show before the microscope, in a longitudinal section, crowded 
parallel fibrils; in a transverse section equally crowded hexagonal cells in 
regular lines, being the cross-cut cavities of the fibrils seen parallel to one 
another in longitudinal sections; and a lucky longitudinal slice shows also 
transverse medullary rays. The definition of all these objects is very clear from 
their blackness, which is owing apparently to very fine charcoal accumulated in 
the region of the cell-walls. In some places, however, these appearances of 
vegetable structure are displaced by little masses of roughly radiated crystallisa- 
tion, obviously the fossilising material substituting its own crystalline arrange- 
ment. 
The structure of the fossil being thus very distinctly shown in small sections 
for the microscope, a successful observation in the case of No. 7 led to a trial 
being made to obtain a demonstration of concentric annual layers on the large 
VOL. XXVIII. PART IT. 31 
