!8o THE FAIRY-LAND OF SCIENCE. 
been preserved even in the coal-bed itself. Do you 
remember our learning in Lecture IV that water 
with lime in it petrifies things, that is, leaves car- 
bonate 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 ob- 
ject? 
Now, it so happens that in a coal-bed at South 
Ouram, near Halifax, in Canada, as well as in some 
other places, carbonate of lime trickled in before the 
plants were turned to coal, and made some round nod- 
ules in the plant-bed, which look like cannon-balls. 
Afterward, 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 petri- 
fied pieces of plants. But many men have spent their 
whole lives in deciphering all the fragments that could 
be found, and though the section given in Fig. 51 
may look to you quite incomprehensible, yet a botanist 
