RECENTLY DISCOVERED IN CRAIGLEITH QUARRY. 215 
known to envelope many fossils of the Coal-measures, has not received from 
geologists the attention which it deserves. Neither the circumstances in which 
it occurs, nor its composition, have been made the subject of inquiry. It 
covers many specimens of Sigillaria, Lepidodendron, and fossilised stems of other 
plants of loose cellular texture, found abundantly in the carboniferous strata 
of the Scottish lowlands ; but it is not always present. A fine Sigillaria from 
Redhall quarry,—where, as will be presently mentioned, a large araucarious fossil 
has been lately found, covered with caking coal,—presents no coaly crust at all, 
either on its surface, or on that of the sandstone mould in which it had lain. 
On the other hand, a lepidodendron from Craigleith quarry, about an inch in 
diameter, is uniformly covered with a very brittle black shining coat, which is 
acted on by heat exactly as the crust of the araucarious fossil, No. 5, and is there- 
fore a very pure caking bituminous coal. I found a similar specimen among seven 
in the Edinburgh Botanic Garden Museum ; and another also among nine, which 
I owe to Dr Dickson, Professor of Botany in Glasgow University. Of the others 
all emitted much dense white flame, and several caked slightly, but some not 
at all. The frothing up, caking, and flaming seemed to be proportional to the 
scantiness of mineral matter in each specimen; but that point was not fixed 
numerically. 
The composition of the great interior mass of these fossils proves to be 
entirely different from that of the thin black crust. Its fracture has a dull- 
grey earthy appearance, like the ordinary limestones of the neighbourhood. 
The density of No. 2 is 2°54, of No. 5, 2°64, of the “branch,” No. 7, 2°88. 
Wiruawm’s fossil, No. 2, when subjected in fragments to the action of diluted 
hydrochloric or nitric acid, effervesces freely like marble; the fluid soon 
becomes black; and, with a sufficiency of acid, nothing is left undissolved 
but an impalpable carbonaceous matter, and a few siliceous particles. The 
silica seems adventitious, because the little particles are large enough to 
feel gritty and to be easily separated, and because they are not met with 
in others of the Craigleith araucarious fossils, such as No. 6. The black 
matter is charcoal, for it burns in a platinum spoon with a red glow, and no 
flame, or a transient, lambent blue flame only ; and there remains 2°1 per cent. 
of loose greyish-red ash, with which acids cause scarcely any effervescence, and 
from which they remove only a trace of lime. It is ordinary charcoal, not 
graphite, because it is dissolved with the aid of powerful oxigenating fluids, 
such as sulphuric acid with chlorate of potash. Hence the carbonaceous 
matter, which partly composes the substance of the fossils, may be regarded as 
vegetable charcoal, with rather more than the usual proportion of earthy 
matters. It is not coal like the carbonaceous crust of the fossils; it contains 
no volatilisable bituminous matter. 
The hydrochloric acid solution, if effected without access of atmospheric air, 
VOL. XXVII. PART Il. 3K 
