7 0 Proceedings of Boyal Society of Edinburgh. [sess. 
probable that this seam is identical in both localities. The thick- 
ness of it varies from 2 feet to 2 feet 3 inches, and contains the 
nodules indiscriminately distributed, and not in any definite layers. 
This bed of coal lies upon an underclay, which in turn rests upon a 
sandstone, the latter being one of the upper members of the mill- 
stone grit formation. 
Above the “hard-bed” seam is a bed of shale about 21 feet thick, 
full of the impressions of shells of undoubted marine genera, such 
as goniatities and aviculopecten. 
The “ coal-balls ” vary in size from about 3 inches to 1 foot in 
their greatest diameter ; they are usually ovoid, slightly flattened 
parallel to the strata, though occasionally spherical ones are found. 
Outwardly they have a black coaly appearance, derived from the 
matrix in which they are embedded, but when broken they present 
a brown or greyish-brown interior, often banded or streaked in 
various ways with bright masses of iron pyrites. 
Up to the year 1883 no analyses of these concretions had been 
published, but in that year I read a paper before the Yorkshire 
Geological and Polytechnic Society and gave two analyses of them, 
which are here reproduced : — 
Analyses of Coal-Balls. 
A. 
B. 
Ferrous oxide, . 
3-21 
0-16 
Oxide of Manganese, 
Trace 
. . . 
Alumina .... 
0-33 
Trace 
Lime, .... 
. 36T7 
46-10 
Magnesia, 
0-88 
0-30 
Silica, .... 
1T6 
1-21 
Sulphuric acid, 
0T5 
0-01 
Chlorine, 
Trace 
Carbonic acid, . 
. 29-00 
35-28 
Phosphoric acid. 
Trace 
Trace 
Iron pyrites, . 
. 21-58 
12-16 
Water, .... 
0-38 
3-00 
Organic matter and loss, . 
7-21 
1-87 
100-00 
100-00 
