A PIECE OF COAL. 177 
destroyed, though people who are used to examining 
with the microscope, can see the crushed remains of 
plants in thin slices of coal. 
But fortunately for us, perfect pieces of plants have 
been preserved even in the coal-bed itself. Do you re- 
member our learning in Lecture IV. that water with 
lime in it petrifies things, that is, leaves carbonate of 
lime to fill up grain by grain the fibres of an animal 
or plant as the living matter decays, and so keeps an 
exact representation of the object ? 
Now, it so happens that in a coal-bed at South 
Ouram, near Halifax, as well as in some other places, 
carbonate of lime trickled in before the plants were 
turned into coal, and made some round nodules in the 
plant-bed, which look like cannon-balls. Afterwards, 
when all the rest of the .bed was turned into coal, these 
round balls remained crystallized, and by cutting thin 
transparent slices across the nodule we can distinctly 
see the leaves and stems and curious little round 
bodies which make up the coal. Several such sections 
may be seen at the British Museum, and when we 
compare these fragments of plants with those which 
we find above and below the coal-bed, we find that 
they agree, thus proving that coal is made of plants, 
and of those plants whose roots grew in the clay floor, 
while their heads reached up far above where the roof 
now is. 
The next question is, what kind of plants were 
these ? Have we anything like them living in the 
world now ? You might perhaps think that it would 
be impossible to decide this question from mere 
petrified pieces of plants. But many men have spent 
