176 THE FAIRY-LAND OF SCIENCE. 
Colliery.* This fossil, which is the cast of a piece of a 
plant, puzzled those who found it for a very long time. 
At last, however, Mr. Binney found the specimen 
growing to the bottom of the trunk of one of the fossil 
trees with spotted stems, called Sigillaria ; and so 
proved that this curious pitted stone is a piece of 
fossil root, or rather underground stem, like that 
which we found in the primrose, and that the little 
pits or dents in it are scars where the rootlets once 
were given off. 
Whole masses of these root-stems, with ribbon-like 
roots lying scattered near them, are found buried in 
the layer of clay called the underclay which makes 
the floor of the coal, and they prove to us that this 
underclay must have been once the ground in which 
the roots of the coal-plants grew. You will feel still 
more sure of this when you find that there is not only 
one straight gallery of coal, but that galleries branch 
out right and left, and that everywhere you find the 
coal lying like a sandwich between the floor and the 
roof, showing that quite a large piece of country must 
be covered by these remains of plants all rooted in the 
underclay. 
But how about the coal itself ? It seems likely, 
when we find roots below and leaves and stems above, 
that the middle is made of plants, but can we prove 
it ? We shall see presently that it has been so 
crushed and altered by being buried deep in the 
ground that the traces of leaves have almost been 
* I am much indebted to Mr. John Williams, of Neath, for pro- 
curing these fossils for me ; and also to Professor Judd for lending me 
some for an earlier lecture. 
